dfs,注意root空的情况
/**
* 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 ans=
0;
void dfs(TreeNode* p,
int x){
if(!p->
left && !p->
right){
ans+=x*
10+p->val;
return;
}
if(p->
left) dfs(p->
left,x*
10+p->val);
if(p->
right) dfs(p->
right,x*
10+p->val);
}
int sumNumbers(TreeNode* root) {
if(!root) return
0;
dfs(root,
0);
return ans;
}
};
