{"group":{"id":1,"name":"Community","lockable":false,"created_at":"2012-01-18T18:02:15.000Z","updated_at":"2026-04-06T14:01:22.000Z","description":"Problems submitted by members of the MATLAB Central community.","is_default":true,"created_by":161519,"badge_id":null,"featured":false,"trending":false,"solution_count_in_trending_period":0,"trending_last_calculated":"2026-04-06T00:00:00.000Z","image_id":null,"published":true,"community_created":false,"status_id":2,"is_default_group_for_player":false,"deleted_by":null,"deleted_at":null,"restored_by":null,"restored_at":null,"description_opc":null,"description_html":null,"published_at":null},"problems":[{"id":1646,"title":"Kurchan 3x3 - Optimal Score","description":"Find an optimal 3x3 Kurchan square, score of 198. \r\n\r\nA 3x3 Kurchan square has values 1:9.The products of each row, column, diagonal, and anti-diagonal are used\r\n\r\nThe Kurchan-value is the Max minus the Minimum of these products.\r\n\r\n*Example: m=[5 1 8;3 9 4;7 2 6]*\r\n\r\nRow Products: 40,108, and 84. Column products 105, 18, and 192.\r\n\r\nDiagonal Products: 270, 1*4*7=28, and 8*3*2=48.\r\n\r\nAnti-Diagonal Products: 8*9*7=504, 1*3*6=18, and 5*4*2=40.\r\n\r\nK is thus 504-18 = 486. [ Max of all products - Min of all products ]\r\n\r\n*Input:* None\r\n\r\n*Output:* Kurchan Square [3x3] that scores 198\r\n\r\nI expect someone to give a min size hardcoded solution at some point.\r\n\r\nRelated Challenges:\r\n\r\n1) \u003chttp://www.mathworks.com/matlabcentral/cody/problems/1634-kurchan-square-evaluation-function Kurchan Square Evaluation\u003e\r\n\r\n2) Minimize Kurchan Squares (N=4:9)\r\n\r\n3) Minimize Kurchan Squares (N=10:20) [Very large numbers]\r\n\r\n4) Maximize Sum of Products (N=4:9) and a Large number Challenge\r\n\r\n5) Minimize Sum of Products (N=4:9) and a Large number Challenge","description_html":"\u003cp\u003eFind an optimal 3x3 Kurchan square, score of 198.\u003c/p\u003e\u003cp\u003eA 3x3 Kurchan square has values 1:9.The products of each row, column, diagonal, and anti-diagonal are used\u003c/p\u003e\u003cp\u003eThe Kurchan-value is the Max minus the Minimum of these products.\u003c/p\u003e\u003cp\u003e\u003cb\u003eExample: m=[5 1 8;3 9 4;7 2 6]\u003c/b\u003e\u003c/p\u003e\u003cp\u003eRow Products: 40,108, and 84. Column products 105, 18, and 192.\u003c/p\u003e\u003cp\u003eDiagonal Products: 270, 1*4*7=28, and 8*3*2=48.\u003c/p\u003e\u003cp\u003eAnti-Diagonal Products: 8*9*7=504, 1*3*6=18, and 5*4*2=40.\u003c/p\u003e\u003cp\u003eK is thus 504-18 = 486. [ Max of all products - Min of all products ]\u003c/p\u003e\u003cp\u003e\u003cb\u003eInput:\u003c/b\u003e None\u003c/p\u003e\u003cp\u003e\u003cb\u003eOutput:\u003c/b\u003e Kurchan Square [3x3] that scores 198\u003c/p\u003e\u003cp\u003eI expect someone to give a min size hardcoded solution at some point.\u003c/p\u003e\u003cp\u003eRelated Challenges:\u003c/p\u003e\u003cp\u003e1) \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/1634-kurchan-square-evaluation-function\"\u003eKurchan Square Evaluation\u003c/a\u003e\u003c/p\u003e\u003cp\u003e2) Minimize Kurchan Squares (N=4:9)\u003c/p\u003e\u003cp\u003e3) Minimize Kurchan Squares (N=10:20) [Very large numbers]\u003c/p\u003e\u003cp\u003e4) Maximize Sum of Products (N=4:9) and a Large number Challenge\u003c/p\u003e\u003cp\u003e5) Minimize Sum of Products (N=4:9) and a Large number Challenge\u003c/p\u003e","function_template":"function m = kurchan_3x3\r\n  m=zeros(3);\r\nend","test_suite":"%%\r\ntic\r\nm = kurchan_3x3\r\ntoc\r\n p=[1     4     7\r\n     2     5     8\r\n     3     6     9\r\n     1     2     3\r\n     4     5     6\r\n     7     8     9\r\n     1     5     9\r\n     4     8     3\r\n     7     2     6\r\n     7     5     3\r\n     8     6     1\r\n     9     4     2];\r\nassert(isequal((1:9)',unique(m(:)))) % check use 1 thru 9\r\nmp=prod(m(p),2);\r\nK=max(mp)-min(mp) % display K score\r\n\r\n% simplified Kurchan scoring for 3x3\r\n\r\nassert(K\u003c=198)  % Pretty certain 198 is best possible, allow better score\r\n\r\n\r\n\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":0,"created_by":3097,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":30,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2013-06-13T04:20:37.000Z","updated_at":"2025-11-27T17:20:36.000Z","published_at":"2013-06-13T05:10:56.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFind an optimal 3x3 Kurchan square, score of 198.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eA 3x3 Kurchan square has values 1:9.The products of each row, column, diagonal, and anti-diagonal are used\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe Kurchan-value is the Max minus the Minimum of these products.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eExample: m=[5 1 8;3 9 4;7 2 6]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eRow Products: 40,108, and 84. Column products 105, 18, and 192.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eDiagonal Products: 270, 1*4*7=28, and 8*3*2=48.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eAnti-Diagonal Products: 8*9*7=504, 1*3*6=18, and 5*4*2=40.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eK is thus 504-18 = 486. [ Max of all products - Min of all products ]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eInput:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e None\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eOutput:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e Kurchan Square [3x3] that scores 198\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI expect someone to give a min size hardcoded solution at some point.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eRelated Challenges:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e1)\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/1634-kurchan-square-evaluation-function\\\"\u003e\u003cw:r\u003e\u003cw:t\u003eKurchan Square Evaluation\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e2) Minimize Kurchan Squares (N=4:9)\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e3) Minimize Kurchan Squares (N=10:20) [Very large numbers]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e4) Maximize Sum of Products (N=4:9) and a Large number Challenge\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e5) Minimize Sum of Products (N=4:9) and a Large number Challenge\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":1237,"title":"It's race time! Write a faster function than the test suite call of unique().","description":"Write a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant. \r\n\r\nExample:\r\nInput: x = [1 1 2 2 3 3];\r\nOutput: [1 2 3];\r\n\r\nInput: x = [0.1 3.1 2.1 2.0 3.1];\r\nOutput: [0.1 3.1 2.1 2.0]; % or any order","description_html":"\u003cp\u003eWrite a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant.\u003c/p\u003e\u003cp\u003eExample:\r\nInput: x = [1 1 2 2 3 3];\r\nOutput: [1 2 3];\u003c/p\u003e\u003cp\u003eInput: x = [0.1 3.1 2.1 2.0 3.1];\r\nOutput: [0.1 3.1 2.1 2.0]; % or any order\u003c/p\u003e","function_template":"function y = my_unique(x)\r\n   y = x;\r\nend","test_suite":"%%\r\nx = rand(10000, 1);\r\nz = rand(10000, 1);\r\nx = vertcat(x, z);\r\ntic\r\ny_correct = unique(x);\r\nt_unique = toc\r\n\r\ntic\r\ny_myunique = my_unique(x);\r\nt_myunique = toc\r\n\r\nassert(isequal(sort(my_unique(x)),y_correct) \u0026\u0026 t_unique \u003e t_myunique)\r\n\r\n%%\r\nx = rand(50000, 1);\r\nz = rand(50000, 1);\r\nx = vertcat(x, z);\r\n\r\ntic\r\ny_correct = unique(x);\r\nt_unique = toc\r\n\r\ntic\r\ny_my_unique = my_unique(x);\r\nt_my_unique = toc\r\n\r\nassert(isequal(sort(my_unique(x)),y_correct) \u0026\u0026 t_unique \u003e t_my_unique)\r\n\r\n%%\r\nx = [1; 2; 3; 4; 2; 3; 4; 5;];\r\n\r\ntic\r\ny_correct = unique(x);\r\nt_unique = toc\r\n\r\ntic\r\ny_my_unique = my_unique(x);\r\nt_my_unique = toc\r\n\r\nassert(isequal(sort(my_unique(x)),y_correct) \u0026\u0026 t_unique \u003e t_my_unique)\r\n\r\n","published":true,"deleted":false,"likes_count":0,"comments_count":9,"created_by":10338,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":31,"test_suite_updated_at":"2013-02-03T20:33:40.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2013-02-01T03:36:13.000Z","updated_at":"2025-09-07T01:43:50.000Z","published_at":"2013-02-01T03:36:13.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eWrite a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eExample: Input: x = [1 1 2 2 3 3]; Output: [1 2 3];\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eInput: x = [0.1 3.1 2.1 2.0 3.1]; Output: [0.1 3.1 2.1 2.0]; % or any order\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"problem_search":{"errors":[],"problems":[{"id":1646,"title":"Kurchan 3x3 - Optimal Score","description":"Find an optimal 3x3 Kurchan square, score of 198. \r\n\r\nA 3x3 Kurchan square has values 1:9.The products of each row, column, diagonal, and anti-diagonal are used\r\n\r\nThe Kurchan-value is the Max minus the Minimum of these products.\r\n\r\n*Example: m=[5 1 8;3 9 4;7 2 6]*\r\n\r\nRow Products: 40,108, and 84. Column products 105, 18, and 192.\r\n\r\nDiagonal Products: 270, 1*4*7=28, and 8*3*2=48.\r\n\r\nAnti-Diagonal Products: 8*9*7=504, 1*3*6=18, and 5*4*2=40.\r\n\r\nK is thus 504-18 = 486. [ Max of all products - Min of all products ]\r\n\r\n*Input:* None\r\n\r\n*Output:* Kurchan Square [3x3] that scores 198\r\n\r\nI expect someone to give a min size hardcoded solution at some point.\r\n\r\nRelated Challenges:\r\n\r\n1) \u003chttp://www.mathworks.com/matlabcentral/cody/problems/1634-kurchan-square-evaluation-function Kurchan Square Evaluation\u003e\r\n\r\n2) Minimize Kurchan Squares (N=4:9)\r\n\r\n3) Minimize Kurchan Squares (N=10:20) [Very large numbers]\r\n\r\n4) Maximize Sum of Products (N=4:9) and a Large number Challenge\r\n\r\n5) Minimize Sum of Products (N=4:9) and a Large number Challenge","description_html":"\u003cp\u003eFind an optimal 3x3 Kurchan square, score of 198.\u003c/p\u003e\u003cp\u003eA 3x3 Kurchan square has values 1:9.The products of each row, column, diagonal, and anti-diagonal are used\u003c/p\u003e\u003cp\u003eThe Kurchan-value is the Max minus the Minimum of these products.\u003c/p\u003e\u003cp\u003e\u003cb\u003eExample: m=[5 1 8;3 9 4;7 2 6]\u003c/b\u003e\u003c/p\u003e\u003cp\u003eRow Products: 40,108, and 84. Column products 105, 18, and 192.\u003c/p\u003e\u003cp\u003eDiagonal Products: 270, 1*4*7=28, and 8*3*2=48.\u003c/p\u003e\u003cp\u003eAnti-Diagonal Products: 8*9*7=504, 1*3*6=18, and 5*4*2=40.\u003c/p\u003e\u003cp\u003eK is thus 504-18 = 486. [ Max of all products - Min of all products ]\u003c/p\u003e\u003cp\u003e\u003cb\u003eInput:\u003c/b\u003e None\u003c/p\u003e\u003cp\u003e\u003cb\u003eOutput:\u003c/b\u003e Kurchan Square [3x3] that scores 198\u003c/p\u003e\u003cp\u003eI expect someone to give a min size hardcoded solution at some point.\u003c/p\u003e\u003cp\u003eRelated Challenges:\u003c/p\u003e\u003cp\u003e1) \u003ca href = \"http://www.mathworks.com/matlabcentral/cody/problems/1634-kurchan-square-evaluation-function\"\u003eKurchan Square Evaluation\u003c/a\u003e\u003c/p\u003e\u003cp\u003e2) Minimize Kurchan Squares (N=4:9)\u003c/p\u003e\u003cp\u003e3) Minimize Kurchan Squares (N=10:20) [Very large numbers]\u003c/p\u003e\u003cp\u003e4) Maximize Sum of Products (N=4:9) and a Large number Challenge\u003c/p\u003e\u003cp\u003e5) Minimize Sum of Products (N=4:9) and a Large number Challenge\u003c/p\u003e","function_template":"function m = kurchan_3x3\r\n  m=zeros(3);\r\nend","test_suite":"%%\r\ntic\r\nm = kurchan_3x3\r\ntoc\r\n p=[1     4     7\r\n     2     5     8\r\n     3     6     9\r\n     1     2     3\r\n     4     5     6\r\n     7     8     9\r\n     1     5     9\r\n     4     8     3\r\n     7     2     6\r\n     7     5     3\r\n     8     6     1\r\n     9     4     2];\r\nassert(isequal((1:9)',unique(m(:)))) % check use 1 thru 9\r\nmp=prod(m(p),2);\r\nK=max(mp)-min(mp) % display K score\r\n\r\n% simplified Kurchan scoring for 3x3\r\n\r\nassert(K\u003c=198)  % Pretty certain 198 is best possible, allow better score\r\n\r\n\r\n\r\n","published":true,"deleted":false,"likes_count":1,"comments_count":0,"created_by":3097,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":30,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2013-06-13T04:20:37.000Z","updated_at":"2025-11-27T17:20:36.000Z","published_at":"2013-06-13T05:10:56.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFind an optimal 3x3 Kurchan square, score of 198.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eA 3x3 Kurchan square has values 1:9.The products of each row, column, diagonal, and anti-diagonal are used\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThe Kurchan-value is the Max minus the Minimum of these products.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eExample: m=[5 1 8;3 9 4;7 2 6]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eRow Products: 40,108, and 84. Column products 105, 18, and 192.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eDiagonal Products: 270, 1*4*7=28, and 8*3*2=48.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eAnti-Diagonal Products: 8*9*7=504, 1*3*6=18, and 5*4*2=40.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eK is thus 504-18 = 486. [ Max of all products - Min of all products ]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eInput:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e None\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eOutput:\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e Kurchan Square [3x3] that scores 198\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eI expect someone to give a min size hardcoded solution at some point.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eRelated Challenges:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e1)\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/matlabcentral/cody/problems/1634-kurchan-square-evaluation-function\\\"\u003e\u003cw:r\u003e\u003cw:t\u003eKurchan Square Evaluation\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e2) Minimize Kurchan Squares (N=4:9)\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e3) Minimize Kurchan Squares (N=10:20) [Very large numbers]\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e4) Maximize Sum of Products (N=4:9) and a Large number Challenge\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e5) Minimize Sum of Products (N=4:9) and a Large number Challenge\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":1237,"title":"It's race time! Write a faster function than the test suite call of unique().","description":"Write a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant. \r\n\r\nExample:\r\nInput: x = [1 1 2 2 3 3];\r\nOutput: [1 2 3];\r\n\r\nInput: x = [0.1 3.1 2.1 2.0 3.1];\r\nOutput: [0.1 3.1 2.1 2.0]; % or any order","description_html":"\u003cp\u003eWrite a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant.\u003c/p\u003e\u003cp\u003eExample:\r\nInput: x = [1 1 2 2 3 3];\r\nOutput: [1 2 3];\u003c/p\u003e\u003cp\u003eInput: x = [0.1 3.1 2.1 2.0 3.1];\r\nOutput: [0.1 3.1 2.1 2.0]; % or any order\u003c/p\u003e","function_template":"function y = my_unique(x)\r\n   y = x;\r\nend","test_suite":"%%\r\nx = rand(10000, 1);\r\nz = rand(10000, 1);\r\nx = vertcat(x, z);\r\ntic\r\ny_correct = unique(x);\r\nt_unique = toc\r\n\r\ntic\r\ny_myunique = my_unique(x);\r\nt_myunique = toc\r\n\r\nassert(isequal(sort(my_unique(x)),y_correct) \u0026\u0026 t_unique \u003e t_myunique)\r\n\r\n%%\r\nx = rand(50000, 1);\r\nz = rand(50000, 1);\r\nx = vertcat(x, z);\r\n\r\ntic\r\ny_correct = unique(x);\r\nt_unique = toc\r\n\r\ntic\r\ny_my_unique = my_unique(x);\r\nt_my_unique = toc\r\n\r\nassert(isequal(sort(my_unique(x)),y_correct) \u0026\u0026 t_unique \u003e t_my_unique)\r\n\r\n%%\r\nx = [1; 2; 3; 4; 2; 3; 4; 5;];\r\n\r\ntic\r\ny_correct = unique(x);\r\nt_unique = toc\r\n\r\ntic\r\ny_my_unique = my_unique(x);\r\nt_my_unique = toc\r\n\r\nassert(isequal(sort(my_unique(x)),y_correct) \u0026\u0026 t_unique \u003e t_my_unique)\r\n\r\n","published":true,"deleted":false,"likes_count":0,"comments_count":9,"created_by":10338,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":31,"test_suite_updated_at":"2013-02-03T20:33:40.000Z","rescore_all_solutions":false,"group_id":1,"created_at":"2013-02-01T03:36:13.000Z","updated_at":"2025-09-07T01:43:50.000Z","published_at":"2013-02-01T03:36:13.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eWrite a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eExample: Input: x = [1 1 2 2 3 3]; Output: [1 2 3];\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003cw:jc w:val=\\\"left\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eInput: x = [0.1 3.1 2.1 2.0 3.1]; Output: [0.1 3.1 2.1 2.0]; % or any order\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"term":"tag:\"toc\"","current_player_id":null,"fields":[{"name":"page","type":"integer","callback":null,"default":1,"directive":null,"facet":null,"facet_method":"and","operator":null,"param":null,"static":null,"prepend":true},{"name":"per_page","type":"integer","callback":null,"default":50,"directive":null,"facet":null,"facet_method":"and","operator":null,"param":null,"static":null,"prepend":true},{"name":"sort","type":"string","callback":null,"default":null,"directive":null,"facet":null,"facet_method":"and","operator":null,"param":null,"static":null,"prepend":true},{"name":"body","type":"text","callback":null,"default":"*:*","directive":null,"facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":false},{"name":"group","type":"string","callback":null,"default":null,"directive":"group","facet":true,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"difficulty_rating_bin","type":"string","callback":null,"default":null,"directive":"difficulty_rating_bin","facet":true,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"id","type":"integer","callback":null,"default":null,"directive":"id","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"tag","type":"string","callback":null,"default":null,"directive":"tag","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"product","type":"string","callback":null,"default":null,"directive":"product","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"created_at","type":"timeframe","callback":{},"default":null,"directive":"created_at","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"profile_id","type":"integer","callback":null,"default":null,"directive":"author_id","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"created_by","type":"string","callback":null,"default":null,"directive":"author","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"player_id","type":"integer","callback":null,"default":null,"directive":"solver_id","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"player","type":"string","callback":null,"default":null,"directive":"solver","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"solvers_count","type":"integer","callback":null,"default":null,"directive":"solvers_count","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"comments_count","type":"integer","callback":null,"default":null,"directive":"comments_count","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"likes_count","type":"integer","callback":null,"default":null,"directive":"likes_count","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"leader_id","type":"integer","callback":null,"default":null,"directive":"leader_id","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true},{"name":"leading_solution","type":"integer","callback":null,"default":null,"directive":"leading_solution","facet":null,"facet_method":"and","operator":null,"param":"term","static":null,"prepend":true}],"filters":[{"name":"asset_type","type":"string","callback":null,"default":null,"directive":null,"facet":null,"facet_method":"and","operator":null,"param":null,"static":"\"cody:problem\"","prepend":true},{"name":"profile_id","type":"integer","callback":{},"default":null,"directive":null,"facet":null,"facet_method":"and","operator":null,"param":"author_id","static":null,"prepend":true}],"query":{"params":{"per_page":50,"term":"tag:\"toc\"","current_player":null,"sort":"map(difficulty_value,0,0,999) asc"},"parser":"MathWorks::Search::Solr::QueryParser","directives":{"term":{"directives":{"tag":[["tag:\"toc\"","","\"","toc","\""]]}}},"facets":{"#\u003cMathWorks::Search::Field:0x00007f234b82a468\u003e":null,"#\u003cMathWorks::Search::Field:0x00007f234b82a3c8\u003e":null},"filters":{"#\u003cMathWorks::Search::Field:0x00007f234b829b08\u003e":"\"cody:problem\""},"fields":{"#\u003cMathWorks::Search::Field:0x00007f234b82a6e8\u003e":1,"#\u003cMathWorks::Search::Field:0x00007f234b82a648\u003e":50,"#\u003cMathWorks::Search::Field:0x00007f234b82a5a8\u003e":"map(difficulty_value,0,0,999) asc","#\u003cMathWorks::Search::Field:0x00007f234b82a508\u003e":"tag:\"toc\""},"user_query":{"#\u003cMathWorks::Search::Field:0x00007f234b82a508\u003e":"tag:\"toc\""},"queried_facets":{}},"query_backend":{"connection":{"configuration":{"index_url":"http://index-op-v2/solr/","query_url":"http://search-op-v2/solr/","direct_access_index_urls":["http://index-op-v2/solr/"],"direct_access_query_urls":["http://search-op-v2/solr/"],"timeout":10,"vhost":"search","exchange":"search.topic","heartbeat":30,"pre_index_mode":false,"host":"rabbitmq-eks","port":5672,"username":"cody-search","password":"78X075ddcV44","virtual_host":"search","indexer":"amqp","http_logging":"true","core":"cody"},"query_connection":{"uri":"http://search-op-v2/solr/cody/","proxy":null,"connection":{"parallel_manager":null,"headers":{"User-Agent":"Faraday v1.0.1"},"params":{},"options":{"params_encoder":"Faraday::FlatParamsEncoder","proxy":null,"bind":null,"timeout":null,"open_timeout":null,"read_timeout":null,"write_timeout":null,"boundary":null,"oauth":null,"context":null,"on_data":null},"ssl":{"verify":true,"ca_file":null,"ca_path":null,"verify_mode":null,"cert_store":null,"client_cert":null,"client_key":null,"certificate":null,"private_key":null,"verify_depth":null,"version":null,"min_version":null,"max_version":null},"default_parallel_manager":null,"builder":{"adapter":{"name":"Faraday::Adapter::NetHttp","args":[],"block":null},"handlers":[{"name":"Faraday::Response::RaiseError","args":[],"block":null}],"app":{"app":{"ssl_cert_store":{"verify_callback":null,"error":null,"error_string":null,"chain":null,"time":null},"app":{},"connection_options":{},"config_block":null}}},"url_prefix":"http://search-op-v2/solr/cody/","manual_proxy":false,"proxy":null},"update_format":"RSolr::JSON::Generator","update_path":"update","options":{"url":"http://search-op-v2/solr/cody"}}},"query":{"params":{"per_page":50,"term":"tag:\"toc\"","current_player":null,"sort":"map(difficulty_value,0,0,999) asc"},"parser":"MathWorks::Search::Solr::QueryParser","directives":{"term":{"directives":{"tag":[["tag:\"toc\"","","\"","toc","\""]]}}},"facets":{"#\u003cMathWorks::Search::Field:0x00007f234b82a468\u003e":null,"#\u003cMathWorks::Search::Field:0x00007f234b82a3c8\u003e":null},"filters":{"#\u003cMathWorks::Search::Field:0x00007f234b829b08\u003e":"\"cody:problem\""},"fields":{"#\u003cMathWorks::Search::Field:0x00007f234b82a6e8\u003e":1,"#\u003cMathWorks::Search::Field:0x00007f234b82a648\u003e":50,"#\u003cMathWorks::Search::Field:0x00007f234b82a5a8\u003e":"map(difficulty_value,0,0,999) asc","#\u003cMathWorks::Search::Field:0x00007f234b82a508\u003e":"tag:\"toc\""},"user_query":{"#\u003cMathWorks::Search::Field:0x00007f234b82a508\u003e":"tag:\"toc\""},"queried_facets":{}},"options":{"fields":["id","difficulty_rating"]},"join":" "},"results":[{"id":1646,"difficulty_rating":"easy-medium"},{"id":1237,"difficulty_rating":"medium-hard"}]}}