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.

/**
 * 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 execute(TreeNode* root,int sum){
        sum-=root->val;
        if(root->left==NULL&&root->right==NULL){
            if(sum==0)
                return true;
        }
        if(root->left&&execute(root->left,sum)){
            return true;
        }
        if(root->right&&execute(root->right,sum)){
            return true;
        }
        return false;
    }
    
    bool hasPathSum(TreeNode* root, int sum) {
        if(root==NULL)
            return false;
        return execute(root,sum); 
    }
};

 

posted @ 2015-10-17 16:02  michaelzhao10  阅读(73)  评论(0编辑  收藏