Sum Root to Leaf Numbers深度优先计算路径和

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

.

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/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
private:
int sum;
public:
void dfs(TreeNode *root,int num){
if(root==NULL)
return;
if(root->left==NULL && root->right==NULL){
num=num*10+root->val;
sum=sum+num;
return;
}
num=num*10+root->val;
dfs(root->left,num);
dfs(root->right,num);
}
int sumNumbers(TreeNode *root) {
sum=0;
dfs(root,0);
return sum;

}
};