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  1. #include<iostream>
  2. #include<stack>
  3. using namespace std;
  4.  
  5. class node{
  6.   public:
  7.   int value;
  8.   node* left;
  9.   node* right;
  10.   node(int value)
  11.   {
  12.     this->value = value;
  13.     left = NULL;
  14.     right = NULL;
  15.   }
  16. };
  17.  
  18. node* preorderToTree(int* a, int length)
  19. {
  20.   if(length==0)
  21.     return NULL;
  22.   node* root = new node(a[0]);
  23.   stack<node*> s;
  24.   s.push(root);
  25.   for(int i=1; i<length; i++)
  26.   {
  27.     node* tmp = new node(a[i]);
  28.     if(tmp->value < s.top()->value)
  29.     {
  30.       s.top()->left = tmp;
  31.     }
  32.     else
  33.     {
  34.       node* popped = NULL;
  35.       while(!s.empty() && tmp->value > s.top()->value)
  36.       {
  37.         popped = s.top();
  38.         s.pop();
  39.       }
  40.       popped->right = tmp;
  41.     }
  42.     s.push(tmp);
  43.   }
  44.   return root;
  45. }
  46.  
  47. void inorder(node* root)
  48. {
  49.   if(root)
  50.   {
  51.     inorder(root->left);
  52.     cout<<root->value<<" ";
  53.     inorder(root->right);
  54.   }
  55. }
  56.  
  57. int main()
  58. {
  59.   int a[] = {10, 8, 5, 2, 6, 7, 9, 20, 15, 25, 23};
  60.   node* root = NULL;
  61.   root = preorderToTree(a, sizeof(a)/sizeof(a[0]));
  62.   inorder(root);
  63. }
Success #stdin #stdout 0.02s 2816KB
comments (?)
stdin 
Standard input is empty
stdout 
2 5 6 7 8 9 10 15 20 23 25
https://ideone.com/VohnS
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

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