Number of Closed Islands problem solved

Author: hasibulislam999

Easy/1254_number-of-closed-islands.js

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+/**
+ * Title: Number of Closed Islands
+ * Description: Given a 2D grid consists of 0s (land) and 1s (water).  An island is a maximal 4-directionally connected group of 0s and a closed island is an island totally (all left, top, right, bottom) surrounded by 1s.
+ * Author: Hasibul Islam
+ * Date: 06/04/2023
+ */
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+var closedIsland = function (grid) {
+  const R = grid.length,
+    C = grid[0].length;
+  const dir = [
+    [1, 0],
+    [-1, 0],
+    [0, 1],
+    [0, -1],
+  ];
+  let counter = 0;
+
+  for (let r = 1; r < R - 1; r++) {
+    for (let c = 1; c < C - 1; c++) {
+      if (!grid[r][c] && isValid(r, c)) counter++;
+    }
+  }
+  return counter;
+
+  function isValid(r, c) {
+    if (grid[r][c]) return true;
+    if (r == 0 || c == 0 || r == R - 1 || c == C - 1) return false;
+    grid[r][c] = 1;
+
+    let result = true;
+
+    for (let [dr, dc] of dir) {
+      if (!isValid(dr + r, dc + c)) result = false;
+    }
+    return result;
+  }
+};
+
+console.log(
+  closedIsland([
+    [1, 1, 0, 0, 0],
+    [1, 1, 0, 0, 0],
+    [0, 0, 0, 1, 1],
+    [0, 0, 0, 0, 0],
+    [0, 0, 0, 0, 0],
+  ])
+);