[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.

解题思路：

题意为判断从根到叶的路径上是否有和为给定的路径。递归即可。注意这种情况，若给出一个空树和0，应该返回false。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool hasPathSum(TreeNode* root, int sum) {
        if(root==NULL){
            return false;
        }
        if(root->left==NULL&&root->right==NULL&&sum==root->val){
            return true;
        }
        if(root->left!=NULL){
            if(hasPathSum(root->left, sum - root->val)){
                return true;
            }
        }
        if(root->right!=NULL){
            if(hasPathSum(root->right, sum - root->val)){
                return true;
            }
        }
        return false;
    }
};

[LeetCode] Path Sum

原文：http://blog.csdn.net/kangrydotnet/article/details/45481439