第十三周：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.

这道题有点遍历的意思，将树遍历一次最后看能不能等于sum。

AC:

/** * Definition for a binary tree node. * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * }; */ bool hasPathSum(struct TreeNode* root, int sum) { if(root==NULL) return false; if(root->left==NULL&&root->right==NULL&&root->val==sum) return true; else return hasPathSum(root->left,sum-root->val)||hasPathSum(root->right,sum-root->val); }