# 13ms to solve this problem

• /**

• 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> boundaryOfBinaryTree(TreeNode
root) {
vector<int> vv;
if(root==NULL){
return vv;
}
stack<TreeNode*> ss;
vv.push_back(root->val);
if(root->left!=NULL){
ss.push(root->left);
}
while(!ss.empty()){
TreeNode* tn= ss.top();
ss.pop();
if(tn->left==NULL&&tn->right == NULL){
vv.push_back(tn->val);
break;
}
vv.push_back(tn->val);
if(tn->right!=NULL){
ss.push(tn->right);
}
if(tn->left != NULL){
ss.push(tn->left);
}
}
while(!ss.empty()){
TreeNode* tn= ss.top();
ss.pop();
if(tn->left==NULL&&tn->right == NULL){
vv.push_back(tn->val);
}
if(tn->right!=NULL){
ss.push(tn->right);
}
if(tn->left != NULL){
ss.push(tn->left);
}
}
stack<int> sss;
while(!ss.empty()){
ss.pop();
}
if(root->right!=NULL){
ss.push(root->right);
}
while(!ss.empty()){
TreeNode* tn= ss.top();
ss.pop();
if(tn->left==NULL&&tn->right == NULL){
sss.push(tn->val);
break;
}
sss.push(tn->val);
if(tn->left != NULL){
ss.push(tn->left);
}
if(tn->right!=NULL){
ss.push(tn->right);
}
}
while(!ss.empty()){
TreeNode* tn= ss.top();
ss.pop();
if(tn->left==NULL&&tn->right == NULL){
sss.push(tn->val);
}
if(tn->left != NULL){
ss.push(tn->left);
}
if(tn->right!=NULL){
ss.push(tn->right);
}
}
while(!sss.empty()){
int i = sss.top();
sss.pop();
vv.push_back(i);
}
return vv;
}
};

Looks like your connection to LeetCode Discuss was lost, please wait while we try to reconnect.