Given a binary tree containing digits from 0⑼ 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.
这个题目很简单，可用递归做：
class Solution {
public:
int sumNumbers(TreeNode *root) {
sum = 0;
sumNumbers(root,0);
return sum;
}
private:
int sum;
void sumNumbers(TreeNode *root,int num) {
if (!root) return;
num = num*10 + root->val;
if (root->left == nullptr && root->right == nullptr) sum += num;
if (root->left) sumNumbers(root->left,num);
if (root->right) sumNumbers(root->right,num);
}
};
