leetcode 112. Path Sum

Seawolf

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.

Note: A leaf is a node with no children.

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 a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    
    public boolean hasPathSum(TreeNode root, int sum) {
        
        if( root == null ) return false;
        
        sum = sum - root.val;
        
        if(root.left == null && root.right == null && sum == 0) return true;
        
        return hasPathSum(root.left, sum) || hasPathSum(root.right, sum);
        
    }
    
}