题解 | 二叉排序树

#include <iostream>
using namespace std;
typedef struct btree{
    int data;
    struct btree *left;
    struct btree *right;
}btree;
btree *insert(btree *t,int x)
{
  if(t==NULL)
  {
    t=new btree;
    t->data=x;
    t->left=t->right=NULL;
  }
  
  if(x<t->data)
  t->left=insert(t->left,x);
  if(x>t->data)
  t->right=insert(t->right,x);
  return t;
}
void preorder(btree *t)
{
  if(t==NULL)
  return;
  cout<<t->data<<" ";
  preorder(t->left);
  preorder(t->right);
}
void inorder(btree *t)
{
  if(t==NULL)
  return;
  inorder(t->left);
  cout<<t->data<<" ";
  inorder(t->right);
}
void postorder(btree *t)
{
  if(t==NULL)
  return;
  postorder(t->left);
  postorder(t->right);
  cout<<t->data<<" ";
}
int main() {
    int n;
    while(cin>>n)
    {btree *root=NULL;
    while(n--)
    {
        int x;cin>>x;
        root=insert(root,x);
    }
    preorder(root);
    cout<<endl;
    inorder(root);
    cout<<endl;
    postorder(root);
    cout<<endl;
    }
}