[Leetcode] 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:

 1 /**
 2  * Definition for binary tree
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public boolean hasPathSum(TreeNode root, int sum) {
12         return dfs(root,sum,0);
13     }
14 
15     private boolean dfs(TreeNode root, int sum, int curSum) {
16         // TODO Auto-generated method stub
17         if(root==null)
18             return false;
19         if(root.left==null&&root.right==null)
20             return (curSum+root.val)==sum;
21         return dfs(root.left,sum,curSum+root.val)||dfs(root.right, sum, curSum+root.val);
22     }
23 }

 

posted @ 2014-11-16 02:47  Phoebe815  阅读(116)  评论(0)  编辑  收藏  举报