LeetCode 40 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 1return true, as there exist a root-to-leaf path 5->4->11->2.
分析：

看见二叉树，想递归。

/**
* 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){
if(sum==root.val)
return true;
else
return false;
}
int remain = sum-root.val;
return hasPathSum(root.left, remain) || hasPathSum(root.right, remain);
}
}