diff --git a/src/WordSearch79.java b/src/WordSearch79.java
deleted file mode 100644
index d9d8914..0000000
--- a/src/WordSearch79.java
+++ /dev/null
@@ -1,50 +0,0 @@
-// Array ,Backtracking, Matrix
-
-import java.util.AbstractMap.SimpleEntry;
-import java.util.Set;
-import java.util.HashSet;
-
-public class WordSearch79 {
-    /*
-        w:length of word
-        Time Complexity : O(m*n*4^w)
-        Space Complexity : O(w)
-     */
-    public boolean dfs(int r, int c, int index, String word, Set<SimpleEntry<Integer, Integer>> visited, char[][] board) {
-        int rows = board.length;
-        int cols = board[0].length;
-        if (index == word.length()) {
-            return true;
-        }
-        if (r < 0 || r == rows || c < 0 || c == cols || visited.contains(new SimpleEntry<>(r, c)) || board[r][c] != word.charAt(index)) {
-            return false;
-        }
-        visited.add(new SimpleEntry<>(r, c));
-        if (this.dfs(r + 1, c, index + 1, word, visited, board) || this.dfs(r - 1, c, index + 1, word, visited, board) || this.dfs(r, c + 1, index + 1, word, visited, board) || this.dfs(r, c - 1, index + 1, word, visited, board)) {
-            return true;
-        }
-        visited.remove(new SimpleEntry<>(r, c));
-        return false;
-    }
-
-    public boolean exist(char[][] board, String word) {
-        int rows = board.length;
-        int cols = board[0].length;
-        Set<SimpleEntry<Integer, Integer>> visited = new HashSet<>();
-        for (int r = 0; r < rows; r++) {
-            for (int c = 0; c < cols; c++) {
-                if (this.dfs(r, c, 0, word, visited, board)) {
-                    return true;
-                }
-            }
-        }
-        return false;
-    }
-
-    public static void main(String[] args) {
-        char[][] board = {{'A', 'B', 'C', 'E'}, {'S', 'F', 'C', 'S'}, {'A', 'D', 'E', 'E'}};
-        String word = "ABCCED";
-        System.out.println(new WordSearch79().exist(board, word));
-        // true
-    }
-}
diff --git a/src/main/java/com/leetcode/medium/WordSearch79.java b/src/main/java/com/leetcode/medium/WordSearch79.java
new file mode 100644
index 0000000..8d1f9ad
--- /dev/null
+++ b/src/main/java/com/leetcode/medium/WordSearch79.java
@@ -0,0 +1,37 @@
+// Tags: Backtracking, DFS
+package com.leetcode.medium;
+
+public class WordSearch79 {
+    private boolean dfs(int r, int c, char[][] board, String word, int index, boolean[][] visited) {
+        if (index == word.length()) {
+            return true;
+        }
+        if (r < 0 || r == board.length || c < 0 || c == board[0].length || visited[r][c] || word.charAt(index) != board[r][c]) {
+            return false;
+        }
+        visited[r][c] = true;
+        if (this.dfs(r + 1, c, board, word, index + 1, visited) || this.dfs(r - 1, c, board, word, index + 1, visited) || this.dfs(r, c + 1, board, word, index + 1, visited) || this.dfs(r, c - 1, board, word, index + 1, visited)) {
+            return true;
+        }
+        visited[r][c] = false;
+        return false;
+    }
+    /*
+        w: length of word
+        Time complexity: O(m*n*4^w)
+        Space complexity: O(w)
+     */
+    public boolean exist(char[][] board, String word) {
+        int rows = board.length;
+        int cols = board[0].length;
+        boolean[][] visited = new boolean[rows][cols];
+        for (int r = 0; r < board.length; r++) {
+            for (int c = 0; c < board[0].length; c++) {
+                if (this.dfs(r, c, board, word, 0, visited)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}
diff --git a/src/test/java/com/leetcode/medium/WordSearch79Test.java b/src/test/java/com/leetcode/medium/WordSearch79Test.java
new file mode 100644
index 0000000..680dcef
--- /dev/null
+++ b/src/test/java/com/leetcode/medium/WordSearch79Test.java
@@ -0,0 +1,51 @@
+package com.leetcode.medium;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.time.Duration;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
+
+public class WordSearch79Test {
+    private WordSearch79 solution;
+
+    @BeforeEach
+    void setUp() {
+        solution = new WordSearch79();
+    }
+
+    @Test
+    void testExist_Example1() {
+        char[][] board = {{'A', 'B', 'C', 'E'}, {'S', 'F', 'C', 'S'}, {'A', 'D', 'E', 'E'}};
+        String word = "ABCCED";
+        boolean expected = true;
+
+        boolean result = assertTimeoutPreemptively(Duration.ofMillis(100), () -> solution.exist(board, word));
+
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testExist_Example2() {
+        char[][] board = {{'A', 'B', 'C', 'E'}, {'S', 'F', 'C', 'S'}, {'A', 'D', 'E', 'E'}};
+        String word = "SEE";
+        boolean expected = true;
+
+        boolean result = assertTimeoutPreemptively(Duration.ofMillis(100), () -> solution.exist(board, word));
+
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testExist_Example3() {
+        char[][] board = {{'A', 'B', 'C', 'E'}, {'S', 'F', 'C', 'S'}, {'A', 'D', 'E', 'E'}};
+        String word = "ABCB";
+        boolean expected = false;
+
+        boolean result = assertTimeoutPreemptively(Duration.ofMillis(100), () -> solution.exist(board, word));
+
+        assertEquals(expected, result);
+    }
+}