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matrix diagonal sum

An old note — I haven't updated it since I wrote it.

Variation from r0bertz

1class Solution:
2    def diagonalSum(self, A: List[List[int]]) -> int:
3        n = len(A)
4        return sum(A[i][i] + A[i][~i] for i in range(n)) - (0, A[n // 2][n // 2])[n % 2]