[LeetCode129]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

.

根据题意，采用深度优先搜索算法，找出所有叶子节点到根节点的的路径，在深搜的同时计算这些路径所代表的数，将这些数存到数组中，最后再对这些数求和。

/**
* 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:
vector<int> v;
int sumNumbers(TreeNode* root) {
v.clear();
int num=0;
dfs(root,num);
int sum=0;
for(int i=0;i<v.size();i++)
{
sum+=v[i];
}
return sum;
}
void dfs(TreeNode* root,int num)
{
if(!root)
return;
if(!root->left&&!root->right)
{
num*=10;
num+=root->val;
v.push_back(num);
}
num*=10;
num+=root->val;
dfs(root->left,num);
dfs(root->right,num);
}
};