LeetCode题解——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.

it's easy to use recursion to solve the problem

/**
 * 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) return false;
        if(!root->left && !root->right) return sum==root->val;
        bool flage = false;
        if(root->left) flage = hasPathSum(root->left,sum-root->val);
        if(flage) return true;
        else{
            if(root->right) return hasPathSum(root->right,sum-root->val);
            else return false;
        }
    } 
};