leetcode 112 Path Sum

Java:

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