add 653

Author: fishercoder1534

README.md

@@ -20,6 +20,7 @@ Your ideas/fixes/algorithms are more than welcome!
 
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|653|[Two Sum IV - Input is a BST](https://leetcode.com/problems/two-sum-iv-input-is-a-bst/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_653.java) |  |  | Easy | Tree
 |652|[Find Duplicate Subtrees](https://leetcode.com/problems/find-duplicate-subtrees/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_652.java) | O(n) |O(n) | Medium | Tree
 |651|[4 Keys Keyboard](https://leetcode.com/problems/4-keys-keyboard/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_651.java) | O(n^2) |O(n) | Medium | DP
 |650|[2 Keys Keyboard](https://leetcode.com/problems/2-keys-keyboard/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_650.java) | O(n^2) |O(n) | Medium | DP

src/main/java/com/fishercoder/solutions/_653.java

@@ -0,0 +1,62 @@
+package com.fishercoder.solutions;
+
+import com.fishercoder.common.classes.TreeNode;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 653. Two Sum IV - Input is a BST
+ *
+ * Given a Binary Search Tree and a target number,
+ * return true if there exist two elements in the BST such that their sum is equal to the given target.
+
+ Example 1:
+ Input:
+    5
+   / \
+  3   6
+ / \   \
+2   4   7
+
+Target = 9
+Output: True
+
+Example 2:
+Input:
+    5
+   / \
+  3   6
+ / \   \
+2   4   7
+
+Target = 28
+Output: False
+
+ */
+public class _653 {
+
+    public static class ListSolution {
+        public boolean findTarget(TreeNode root, int k) {
+            if (root == null) return false;
+            List<Integer> list = new ArrayList<>();
+            dfs(root, list);
+            for (int i = 0; i < list.size() - 1; i++) {
+                for (int j = i + 1; j < list.size(); j++) {
+                    if (list.get(i) + list.get(j) == k) return true;
+                }
+            }
+            return false;
+        }
+
+        private void dfs(TreeNode root, List<Integer> list) {
+            list.add(root.val);
+            if (root.left != null) {
+                dfs(root.left, list);
+            }
+            if (root.right != null) {
+                dfs(root.right, list);
+            }
+        }
+    }
+}

src/test/java/com/fishercoder/_653Test.java

@@ -0,0 +1,75 @@
+package com.fishercoder;
+
+import com.fishercoder.common.classes.TreeNode;
+import com.fishercoder.solutions._653;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static junit.framework.Assert.assertEquals;
+
+public class _653Test {
+    private static _653.ListSolution listSolution;
+    private static boolean expected;
+    private static TreeNode root;
+
+    @BeforeClass
+    public static void setup(){
+        listSolution = new _653.ListSolution();
+    }
+
+    @Before
+    public void setupForEachTest(){
+        root = null;
+    }
+
+    @Test
+    public void test1(){
+        root = new TreeNode(5);
+        root.left = new TreeNode(3);
+        root.left.left = new TreeNode(2);
+        root.left.right = new TreeNode(4);
+        root.right = new TreeNode(6);
+        root.right.right = new TreeNode(7);
+        expected = true;
+        assertEquals(expected, listSolution.findTarget(root, 9));
+    }
+
+    @Test
+    public void test2(){
+        root = new TreeNode(2);
+        root.left = new TreeNode(1);
+        root.right = new TreeNode(3);
+        expected = true;
+        assertEquals(expected, listSolution.findTarget(root, 4));
+    }
+
+    @Test
+    public void test3(){
+        root = new TreeNode(1);
+        expected = false;
+        assertEquals(expected, listSolution.findTarget(root, 2));
+    }
+
+    @Test
+    public void test4(){
+        root = new TreeNode(2);
+        root.left = new TreeNode(0);
+        root.left.left = new TreeNode(-4);
+        root.left.right = new TreeNode(1);
+        root.right = new TreeNode(3);
+        expected = true;
+        assertEquals(expected, listSolution.findTarget(root, -1));
+    }
+
+    @Test
+    public void test5(){
+        TreeNode root = new TreeNode(2);
+        root.left = new TreeNode(1);
+        root.right = new TreeNode(3);
+        root.left.left = new TreeNode(-4);
+        root.left.left.right = new TreeNode(0);
+        expected = true;
+        assertEquals(expected, listSolution.findTarget(root, 2));
+    }
+}