Two Sum IV - Input is a BST : Accepted

Author: gouthampradhan

README.md

@@ -247,6 +247,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Diameter of Binary Tree](problems/src/tree/DiameterOfBinaryTree.java) (Easy)
 - [Binary Tree Paths](problems/src/tree/BinaryTreePaths.java) (Easy)
 - [Sum of Left Leaves](problems/src/tree/SumofLeftLeaves.java) (Easy)
+- [Two Sum IV - Input is a BST](problems/src/tree/TwoSumIV.java) (Easy)
 
 #### [Two Pointers](problems/src/two_pointers)
 

problems/src/tree/TwoSumIV.java

@@ -0,0 +1,70 @@
+package tree;
+
+import java.util.HashSet;
+
+/**
+ * Created by gouthamvidyapradhan on 16/12/2017.
+ * 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 TwoSumIV {
+
+    public class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+        TreeNode(int x) { val = x; }
+    }
+
+    /**
+     * Main method
+     * @param args
+     * @throws Exception
+     */
+    public static void main(String[] args) throws Exception{
+    }
+
+    public boolean findTarget(TreeNode root, int k) {
+       return inorder(root, new HashSet<>(), k);
+    }
+
+    private boolean inorder(TreeNode node, HashSet<Integer> set, int k){
+        if(node != null){
+            int req = k - (node.val);
+            if(set.contains(req)){
+                return true;
+            }
+            set.add(node.val);
+            if(inorder(node.left, set, k)){
+                return true;
+            } else{
+                if(inorder(node.right, set, k)){
+                    return true;
+                }
+            }
+        } return false;
+    }
+}