Number of Enclaves problem solved

Author: hasibulislam999

Easy/1020_number-of-enclaves.js

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+/**
+ * Title: Number of Enclaves
+ * Description: You are given an m x n binary matrix grid, where 0 represents a sea cell and 1 represents a land cell.
+ * Author: Hasibul Islam
+ * Date: 07/04/2023
+ */
+
+/**
+ * @param {number[][]} grid
+ * @return {number}
+ */
+function numEnclaves(grid) {
+  const m = grid.length;
+  const n = grid[0].length;
+  const visited = Array(m)
+    .fill()
+    .map(() => Array(n).fill(false));
+
+  // mark all boundary land cells as reachable
+  for (let i = 0; i < m; i++) {
+    dfs(i, 0);
+    dfs(i, n - 1);
+  }
+  for (let j = 0; j < n; j++) {
+    dfs(0, j);
+    dfs(m - 1, j);
+  }
+
+  // count the number of unreachable land cells
+  let count = 0;
+  for (let i = 0; i < m; i++) {
+    for (let j = 0; j < n; j++) {
+      if (grid[i][j] === 1 && !visited[i][j]) {
+        count++;
+      }
+    }
+  }
+  return count;
+
+  function dfs(i, j) {
+    if (
+      i < 0 ||
+      i >= m ||
+      j < 0 ||
+      j >= n ||
+      visited[i][j] ||
+      grid[i][j] === 0
+    ) {
+      return;
+    }
+    visited[i][j] = true;
+    dfs(i - 1, j);
+    dfs(i + 1, j);
+    dfs(i, j - 1);
+    dfs(i, j + 1);
+  }
+}
+
+const grid = [
+  [0, 0, 0, 0],
+  [1, 0, 1, 0],
+  [0, 1, 1, 0],
+  [0, 0, 0, 0],
+];
+
+console.log(numEnclaves(grid)); // Output: 3