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MatrixDiagonalSum.ts
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MatrixDiagonalSum.ts
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// Source : https://leetcode.com/problems/matrix-diagonal-sum/
// Author : squxq
// Date : 2023-10-24
/*****************************************************************************************************
*
* Given a square matrix mat, return the sum of the matrix diagonals.
*
* Only include the sum of all the elements on the primary diagonal and all the elements on the
* secondary diagonal that are not part of the primary diagonal.
*
* Example 1:
*
* Input: mat = [[1,2,3],
* [4,5,6],
* [7,8,9]]
* Output: 25
* Explanation: Diagonals sum: 1 + 5 + 9 + 3 + 7 = 25
* Notice that element mat[1][1] = 5 is counted only once.
*
* 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
******************************************************************************************************/
/* eslint-disable @typescript-eslint/no-non-null-assertion */
export function diagonalSum(mat: number[][]): number {
let sum: number = 0;
const len: number = mat.length;
for (let i: number = 0; i < len; i++) {
for (let j: number = 0; j < len; j++) {
if (i === j || i + j === len - 1) sum += mat[i]![j]!;
}
}
return sum;
}