Create 1314-matrix-block-sum.js

Author: everthis

1314-matrix-block-sum.js

@@ -0,0 +1,25 @@
+/**
+ * @param {number[][]} mat
+ * @param {number} k
+ * @return {number[][]}
+ */
+const matrixBlockSum = function(mat, k) {
+  const m = mat.length, n = mat[0].length
+  const rangeSum = Array.from({ length: m + 1 }, () => Array(n + 1).fill(0))
+
+  for(let i = 0; i < m; i++) {
+    for(let j = 0; j < n; j++) {
+      rangeSum[i + 1][j + 1] = rangeSum[i + 1][j] + rangeSum[i][j + 1] - rangeSum[i][j] + mat[i][j]
+    }
+  }
+  const res = Array.from({ length: m }, () => Array(n).fill(0))
+  for(let i = 0; i < m; i++) {
+    for(let j = 0; j < n; j++) {
+      let r1 = Math.max(0, i - k), c1 = Math.max(0, j - k)
+      let r2 = Math.min(m, i + k + 1), c2 = Math.min(n, j + k + 1)
+      res[i][j] = rangeSum[r2][c2] - rangeSum[r2][c1] - rangeSum[r1][c2] + rangeSum[r1][c1]
+    }
+  }
+
+  return res
+};