14
08/2015
[LeetCode] Sum Root to Leaf Numbers
Sum Root to Leaf Numbers
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.
For example,
1 / \ 2 3
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Return the sum = 12 + 13 = 25.
解题思路：
这道题的意思是每条从根到叶的数字组成一个数，然后所有的数加起来。
一个好的办法就是递归。
/**
* 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 sumNumbers(TreeNode* root) {
int result = 0;
helper(root, 0, result);
return result;
}
void helper(TreeNode* root, int temp, int& result){
if(root==NULL){
return;
}
temp = temp*10;
temp = temp + root->val;
if(root->left==NULL && root->right==NULL){
result += temp;
}
helper(root->left, temp, result);
helper(root->right, temp, result);
}
};
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