LeetCode OJ 129. Sum Root to Leaf Numbers
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
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