LeetCode[Tree]: Path Sum

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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. 
For example: 
Given the below binary tree and sum = 22,


return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

这个题目非常适合用递归来做,C++代码实现非常简单:

    bool hasPathSum(TreeNode *root, int sum) {        if (!root) return false;        if (root->left  && hasPathSum(root->left,  sum - root->val)) return true;        if (root->right && hasPathSum(root->right, sum - root->val)) return true;        if (root->left == nullptr && root->right == nullptr && root->val == sum) return true;        return false;    }

时间性能如下图所示:


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