Problem 659. How long is the longest prime diagonal?

Stanislaw Ulam once observed that if the counting numbers are arranged in a spiral, the prime numbers contained in it form a surprising pattern. They appear to cluster along diagonals of the spiral matrix.
Given n, return the length of the longest diagonal sequence of primes in spiral(n).
Example:
Input n = 7
Output d = 4
Since isprime(spiral(n)) is
1 0 0 0 1 0 0
0 0 0 1 0 0 0
1 0 1 0 0 0 0
0 1 0 0 1 1 0
0 0 1 0 1 0 1
0 1 0 0 0 1 0
1 0 0 0 0 0 1

Solution Stats

39.74% Correct | 60.26% Incorrect
Last Solution submitted on May 22, 2024

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