PathSum

Change-Id: I9759d8750b60737cadb1ba0ca44479a8fdce7194

Author: applewjg

PathSum.java

@@ -0,0 +1,41 @@
+/*
+ Author:     Annie Kim, [email protected]
+ Date:       Apr 6, 2013
+ Update:     Jul 26, 2013
+ Problem:    Path Sum
+ Difficulty: easy
+ Source:     http://www.leetcode.com/onlinejudge
+ Notes:
+ Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up 
+ all the values along the path equals the given sum.
+
+ For example:
+ Given the below binary tree and sum = 22,
+              5
+             / \
+            4   8
+           /   / \
+          11  13  4
+         /  \      \
+        7    2      1
+ return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
+ 
+ Solution: Recursion.
+ */
+/**
+ * Definition for binary tree
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+public class Solution {
+    public boolean hasPathSum(TreeNode root, int sum) {
+        if (root == null) return false;
+        if (root.left == null && root.right == null) return sum == root.val;
+        return hasPathSum(root.left, sum - root.val) || 
+               hasPathSum(root.right, sum - root.val);
+    }
+}