diff --git a/solution/0200-0299/0200.Number of Islands/README.md b/solution/0200-0299/0200.Number of Islands/README.md
index 634d42f1eb971..87e54186056f9 100644
--- a/solution/0200-0299/0200.Number of Islands/README.md	
+++ b/solution/0200-0299/0200.Number of Islands/README.md	
@@ -208,20 +208,19 @@ function numIslands(grid: string[][]): number {
     const m = grid.length;
     const n = grid[0].length;
     let ans = 0;
-    function dfs(i, j) {
-        grid[i][j] = '0';
-        const dirs = [-1, 0, 1, 0, -1];
-        for (let k = 0; k < 4; ++k) {
-            const x = i + dirs[k];
-            const y = j + dirs[k + 1];
-            if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == '1') {
-                dfs(x, y);
-            }
+    const dfs = (i: number, j: number) => {
+        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 < m; ++i) {
         for (let j = 0; j < n; ++j) {
-            if (grid[i][j] == '1') {
+            if (grid[i][j] === '1') {
                 dfs(i, j);
                 ++ans;
             }
diff --git a/solution/0200-0299/0200.Number of Islands/README_EN.md b/solution/0200-0299/0200.Number of Islands/README_EN.md
index e2efa41f09937..6af18eb748ddf 100644
--- a/solution/0200-0299/0200.Number of Islands/README_EN.md	
+++ b/solution/0200-0299/0200.Number of Islands/README_EN.md	
@@ -198,20 +198,19 @@ function numIslands(grid: string[][]): number {
     const m = grid.length;
     const n = grid[0].length;
     let ans = 0;
-    function dfs(i, j) {
-        grid[i][j] = '0';
-        const dirs = [-1, 0, 1, 0, -1];
-        for (let k = 0; k < 4; ++k) {
-            const x = i + dirs[k];
-            const y = j + dirs[k + 1];
-            if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == '1') {
-                dfs(x, y);
-            }
+    const dfs = (i: number, j: number) => {
+        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 < m; ++i) {
         for (let j = 0; j < n; ++j) {
-            if (grid[i][j] == '1') {
+            if (grid[i][j] === '1') {
                 dfs(i, j);
                 ++ans;
             }
diff --git a/solution/0200-0299/0200.Number of Islands/Solution.ts b/solution/0200-0299/0200.Number of Islands/Solution.ts
index b398e93559c7b..8ac5367be98ac 100644
--- a/solution/0200-0299/0200.Number of Islands/Solution.ts	
+++ b/solution/0200-0299/0200.Number of Islands/Solution.ts	
@@ -2,20 +2,19 @@ function numIslands(grid: string[][]): number {
     const m = grid.length;
     const n = grid[0].length;
     let ans = 0;
-    function dfs(i, j) {
-        grid[i][j] = '0';
-        const dirs = [-1, 0, 1, 0, -1];
-        for (let k = 0; k < 4; ++k) {
-            const x = i + dirs[k];
-            const y = j + dirs[k + 1];
-            if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == '1') {
-                dfs(x, y);
-            }
+    const dfs = (i: number, j: number) => {
+        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 < m; ++i) {
         for (let j = 0; j < n; ++j) {
-            if (grid[i][j] == '1') {
+            if (grid[i][j] === '1') {
                 dfs(i, j);
                 ++ans;
             }