add solution: number-of-islands

Author: yihyun-kim1

number-of-islands/yihyun-kim1.js

@@ -0,0 +1,30 @@
+/**
+ * @param {character[][]} grid
+ * @return {number}
+ */
+var numIslands = function (grid) {
+  let count = 0;
+
+  const dfs = (i, j) => {
+    if (i < 0 || i >= grid.length || j < 0 || j >= grid[0].length) return;
+    if (grid[i][j] !== "1") return;
+
+    grid[i][j] = "0";
+
+    dfs(i + 1, j);
+    dfs(i - 1, j);
+    dfs(i, j + 1);
+    dfs(i, j - 1);
+  };
+
+  for (let i = 0; i < grid.length; i++) {
+    for (let j = 0; j < grid[0].length; j++) {
+      if (grid[i][j] === "1") {
+        dfs(i, j);
+        count++;
+      }
+    }
+  }
+
+  return count;
+};