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);}