LeetCode----Path Sum

Path Sum Total Accepted: 9765 Total Submissions: 32502 My Submissions
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.

题目链接

这是我的代码：

主要的注意点是要考虑 root = NULL的情况

/**
 * Definition for binary tree
 * 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 == NULL) return false;
        if (root->left == NULL and root->right == NULL)
            return root->val == sum ? true : false;
        if (root->left != NULL and hasPathSum(root->left, sum-(root->val)))
            return true;
        if (root->right != NULL and hasPathSum(root->right, sum-(root->val)))
            return true;
        return false;
    }
};

这是我的Python代码：

class Solution:
    # @param root, a tree node
    # @param sum, an integer
    # @return a boolean
    def hasPathSum(self, root, sum):
        if root is None:
            return False
        if root.left is None and root.right is None:
            return True if root.val == sum else False
        if root.left != None and self.hasPathSum(root.left, sum-(root.val)):
            return True
        if root.right != None and self.hasPathSum(root.right, sum-(root.val)):
            return True
        return False

Python的速度大约是C++的1/5到1/4