add a solution for 653

fishercoder1534 · fishercoder1534 · commit ea2de74ec135 · 2021-08-23T08:11:28.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_653.java b/src/main/java/com/fishercoder/solutions/_653.java
@@ -3,7 +3,9 @@
 import com.fishercoder.common.classes.TreeNode;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 public class _653 {
 
@@ -34,4 +36,22 @@ private void dfs(TreeNode root, List<Integer> list) {
             }
         }
     }
+
+    public static class Solution2 {
+        public boolean findTarget(TreeNode root, int k) {
+            return dfs(root, new HashSet(), k);
+        }
+
+        private boolean dfs(TreeNode root, Set<Integer> set, int k) {
+            if (root == null) {
+                return false;
+            }
+
+            if (set.contains(k - root.val)) {
+                return true;
+            }
+            set.add(root.val);
+            return dfs(root.left, set, k) || dfs(root.right, set, k);
+        }
+    }
 }
