[leetcode] 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

.

递归咯~ 返回条件就是当前节点为叶子节点，结算一下

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

}

int sumNumbers(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
ret = 0;

if(!root) return 0;
num(root, 0);
return ret;
}
};