Matrix Diagonal Sum

EasyAlgorithms

Description

Given a square matrix `mat`, return the sum of the matrix diagonals. Include the sum of all the elements on the **primary diagonal** (top-left to bottom-right) and all the elements on the **secondary diagonal** (top-right to bottom-left) that are **not** part of the primary diagonal.

Example 1

Input: mat = [[1,2,3],[4,5,6],[7,8,9]]

Output: 25

Explanation: Primary diagonal: 1 + 5 + 9 = 15. Secondary diagonal: 3 + 7 = 10 (the center 5 is counted only once). Total 25.

Example 2

Input: mat = [[1,1,1,1],[1,1,1,1],[1,1,1,1],[1,1,1,1]]

Output: 8

Example 3

Input: mat = [[5]]

Output: 5

Constraints

- n == mat.length == mat[i].length - 1 <= n <= 100 - 1 <= mat[i][j] <= 100

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