fork download
copy 
  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. struct TreeNode{
  4. 	int val;
  5. 	TreeNode* right;
  6. 	TreeNode* left;
  7. 	TreeNode(int val):left(nullptr),right(nullptr),val(val){};
  8. };
  9.  
  10. vector<int>top(TreeNode* root){
  11.   vector<int>ans;
  12.   if(root == nullptr)return ans;
  13.  
  14.   queue<TreeNode*>q;
  15.   q.push(root);
  16.  
  17.   while(!q.empty()){
  18.   	int size = q.size();
  19.  
  20.   	for(int i = 0;i<size;i++){
  21.   	auto u= q.front();
  22.   	q.pop();
  23.  
  24.   	if(i == size-1)ans.push_back(u->val);	
  25.  
  26.   	if(u->left){
  27.   		q.push(u->left);
  28.   	}
  29.  
  30.   	if(u->right){
  31.   		q.push(u->right);
  32.   	}
  33.   }
  34.   }
  35.  
  36.   return ans;
  37. }
  38. TreeNode* buildTree(){
  39. 	int x;cin>>x;
  40. 	if(x==-1)return nullptr;
  41. 	TreeNode* root = new TreeNode(x);
  42.  
  43. 	queue<TreeNode*>q;
  44. 	q.push(root);
  45.  
  46. 	while(!q.empty()){
  47. 		auto u = q.front();
  48. 		q.pop();
  49.  
  50. 		if(cin>>x && x!=-1){
  51. 			u->left = new TreeNode(x);
  52. 			q.push(u->left);
  53. 		}
  54.  
  55. 		if(cin>>x && x!=-1){
  56. 			u->right = new TreeNode(x);
  57. 			q.push(u->right);
  58. 		}
  59. 	}
  60. 	return root;
  61. }
  62. int main() {
  63.     TreeNode* root = buildTree();
  64.    vector<int>ans = top(root);
  65.  
  66.     for(auto x : ans){
  67.  
  68.     	cout<<x<<endl;
  69.     }
  70. 	return 0;
  71. }
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
copy 
1 2 3 6 5 8 4
stdout
copy 
1
3
4
https://ideone.com/J8II4y
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!