Problem 56060. Sub-Diagonal Sum

Dyuman Joshi

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Given a (m x n) matrix and a value r {1,-1}, change every element to the sum of the diagonal led by the element.
r=1 > regular diagonal (top left to bottom right)
r=-1 > flipped/cross diagonal (top right to bottom left)
in=[1 2 3 4
    5 6 7 8
    1 3 2 0]
r=1
out=[9  9  11 4
     8  8  7  8
     1  3  2  0]
%explaination
(1,1) diagonal - [1 6 2], sum = 9
(1,3) diagonal - [3 8], sum = 11
(2,1) diagonal - [5 3], sum = 8
(2,4) diagonal - [8], sum = 8
in=[1 -2  3 -4
    5 -6  7 -8
    1  3 -2  0]
r=-1
out=[1  3 -2   6
     5 -5 10 -10
     1  3 -2   0]
%explaination
(1,1) diagonal - [1], sum = 1
(1,3) diagonal - [3 -6 1], sum = -2
(2,2) diagonal - [-6 1], sum = -5
(2,4) diagonal - [-8 -2], sum = -10