[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.

 

递归深搜，一类题。解法和Sum Root to Leaf Numbers一样。

/**
 * 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:
    void dfs(TreeNode* root,int sum,int add,bool& has)
    {
        add+=root->val;
        if(root->left==NULL && root->right==NULL)
        {
            if(add==sum)
            {
                has=true;
                return;
            }
        }
        if(root->left) dfs(root->left,sum,add,has);
        if(root->right) dfs(root->right,sum,add,has);
        
    }
    bool hasPathSum(TreeNode* root, int sum) {
        if(!root) return false;
        int add=0;
        bool result=false;
        dfs(root,sum,add,result);
        return result;
    }
};