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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. struct TreeNode{
  5. 	TreeNode* left;
  6. 	TreeNode* right;
  7.  
  8. 	int data;
  9. 	TreeNode(int val):left(nullptr),right(nullptr),data(val){};
  10. };
  11.  
  12. vector<int>preT(TreeNode* root){
  13. 	vector<int>pre;
  14. 		if(root == nullptr)
  15.         return pre;
  16. 	stack<TreeNode*>st;
  17.  
  18. 	st.push(root);
  19.  
  20. 	while(!st.empty()){
  21. 		auto node = st.top();st.pop();
  22.  
  23. 		pre.push_back(node->data);
  24.  
  25. 	    if(node->right){
  26. 	    	st.push(node->right);
  27. 	    }
  28.  
  29. 	    if(node->left){
  30. 	    	st.push(node->left);
  31. 	    }
  32. 	}
  33.  
  34. return pre;	
  35. }
  36.  
  37. TreeNode* buildTree(){
  38. 	int x;
  39. 	cin>>x;
  40. 	if(x==-1)return nullptr;
  41. 	TreeNode* root = new TreeNode(x);
  42. 	queue<TreeNode*>st;
  43. 	st.push(root);
  44.  
  45. 	while(!st.empty()){
  46. 		auto node = st.front();st.pop();
  47.  
  48.  
  49. 		if(cin>>x && x != -1){
  50. 			node->left = new TreeNode(x);
  51. 			st.push(node->left);
  52. 		}
  53.  
  54.  
  55. 		if(cin>>x && x != -1){
  56. 			node->right = new TreeNode(x);
  57. 			st.push(node->right);
  58. 		}
  59. 	}
  60. 	return root;
  61. }
  62.  
  63. int main() {
  64.     TreeNode* root = buildTree();
  65.     vector<int>pre = preT(root);
  66.     for(int x:pre)cout<< x <<" ";
  67. 	return 0;
  68. }
Success #stdin #stdout 0s 5312KB
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https://ideone.com/odTm8L
language:
C++14 (gcc 8.3)
created:
58 minutes ago
visibility:
public

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