✨ matrix diagonal sum

Author: tangweikun

src/1572-matrix-diagonal-sum/index.js

@@ -0,0 +1,13 @@
+var diagonalSum = function (mat) {
+  const n = mat.length;
+  const mid = Math.floor(n / 2);
+  let sum = 0;
+
+  // 逐行遍历，每行前后各经过一个
+  for (let i = 0; i < n; i++) {
+    sum += mat[i][i] + mat[i][n - 1 - i];
+  }
+
+  // 奇数方阵需要去除重复项
+  return sum - mat[mid][mid] * (n & 1);
+};