leetcode -- Path Sum

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.

Solution:

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

        return hasPathSum(root.left, sum-root.val) || hasPathSum(root.right, sum-root.val);

    }
}