add: number of islands

Author: HerrineKim

number-of-islands/HerrineKim.js

@@ -0,0 +1,35 @@
+/**
+ * @param {character[][]} grid
+ * @return {number}
+ */
+var numIslands = function (grid) {
+  if (!grid || grid.length === 0) return 0;
+
+  const rows = grid.length;
+  const cols = grid[0].length;
+  let islandCount = 0;
+
+  const dfs = (row, col) => {
+    if (row < 0 || row >= rows || col < 0 || col >= cols || grid[row][col] === '0') {
+      return;
+    }
+
+    grid[row][col] = '0';
+
+    dfs(row - 1, col);
+    dfs(row + 1, col);
+    dfs(row, col - 1);
+    dfs(row, col + 1);
+  };
+
+  for (let i = 0; i < rows; i++) {
+    for (let j = 0; j < cols; j++) {
+      if (grid[i][j] === '1') {
+        islandCount++;
+        dfs(i, j);
+      }
+    }
+  }
+
+  return islandCount;
+};