Path Sum

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.

Java

public class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
        if(root == null) {
            return false;
        }

        int newSum = sum - root.val;

        if(root.left == null && root.right == null) {
            return newSum == 0;
        } else if (root.left == null) {
            return hasPathSum(root.right, newSum);
        } else if(root.right == null) {
            return hasPathSum(root.left, newSum);
        } else {
            return hasPathSum(root.left, newSum) || hasPathSum(root.right, newSum);
        }
    }
}