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112. 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.

 

一开始被这题目坑了,因为叶子节点的左右孩子都是NULL  后捞改了一下代码  过了

/** * 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 hasPathSum1(TreeNode* root, int sum) {        if (root == NULL){            if (sum == 0) return true;            return false;        }        if (root->left == NULL) return hasPathSum1(root->right,sum - root->val);        else if (root->right == NULL) return hasPathSum1(root->left,sum - root->val);        else return  (hasPathSum1(root->left,sum - root->val) || hasPathSum1(root->right,sum - root->val));    }    bool hasPathSum(TreeNode* root, int sum) {        if (root == NULL) return false;        return hasPathSum1(root, sum);    }};
/** * 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(sum == root->val && root->left==NULL &&root->right == NULL) return true;                 return hasPathSum(root->left, sum-root->val)||hasPathSum(root->right, sum-root->val);            }};

 

112. Path Sum