leetcode112. Path Sum路径之和 递归

 

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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.

Note: A leaf is a node with no children.

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 hasPathSum(TreeNode* root, int sum) {
       return  helper(root,sum);
        
    }
   private:
       bool helper(TreeNode *root,int sum)
    {
        if(root==NULL)
           return false;
        if(!root->left&&!root->right&&sum-root->val==0)
            return true;
      return(helper(root->left,sum-root->val)|| helper(root->right,sum-root->val));

            
    }
};