Path Sum.java

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.

/**
 * 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 && root.val == sum) return true;
	boolean l = root.left != null ? hasPathSum(root.left, sum - root.val) : false;
	boolean r = root.right != null ? hasPathSum(root.right, sum - root.val) : false;
	return l || r;
    }
}