题目
Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.
An example is the root-to-leaf path 1->2->3 which represents the number 123.
Find the total sum of all root-to-leaf numbers.
Note: A leaf is a node with no children.
- Example:
- Input: [1,2,3]
- 1
- / 2 3
- Output: 25
- Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.
- Example 2:
- Input: [4,9,0,5,1]
- 4
- / 9 0
- / 5 1
- Output: 1026
- Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.
解答
今天又选了一道水题, 就是二叉树的先序遍历, 又是一遍 AC... 感觉这种题目都不用动脑子, 明天选一道要动脑子的题目.
下面是 AC 的代码:
- /**
- * 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:
- int sum = 0;
- int temp = 0;
- void preorder(TreeNode *node){
- if(node == NULL){
- return ;
- }
- temp = temp * 10 + node->val;
- if(node->left == NULL && node->right == NULL){
- sum += temp;
- }
- else{
- preorder(node->left);
- preorder(node->right);
- }
- temp = (temp - node->val) / 10;
- return ;
- }
- int sumNumbers(TreeNode* root) {
- preorder(root);
- return sum;
- }
- };
- 138
来源: http://www.bubuko.com/infodetail-2592820.html