LeetCode 1572. Matrix Diagonal Sum

問題：將矩陣的斜對角所映射到的數值相加
解法：找到對應位置進行相加
JavaScript

/**
 * @param {number[][]} mat
 * @return {number}
 */
var diagonalSum = function (mat) {
    const length = mat.length;
    let sum = 0;

    for (let i = 0; i < length; i++) {
        sum += mat[i][i]
        sum += mat[length - i - 1][i]
    }

    if (length % 2 == 1) {
        sum -= mat[Math.floor(length / 2)][Math.floor(length / 2)];
    }

    return sum;
}