二叉排序树

• 测试用例中有重复数据，应忽略这些数据（题意）

  #include<iostream>
  #include <string>
  using namespace std;
  struct TreeNode{
    int s;
    TreeNode * left;
    TreeNode * right;
    TreeNode(int c):s(c),left(NULL), right(NULL){}
  };
  TreeNode* insert(TreeNode *pos, int x){
    if(pos == NULL){
        pos = new TreeNode(x);      
    } else if( x > pos->s ){
        pos->right = insert(pos->right, x);
    } else if( x < pos->s ){
        pos->left = insert(pos->left, x);
    }
    return pos;
  }
  void preorder(TreeNode *root){
    if(root == NULL) return;
    cout << root->s<< " ";
    preorder(root->left);
    preorder(root->right);
    return;
  }
  void inorder(TreeNode *root){
    if(root == NULL) return; 
    inorder(root->left);
    cout << root->s<< " ";
    inorder(root->right);
    return;
  }
  void postorder(TreeNode *root){
    if(root == NULL) return;
    postorder(root->left);
    postorder(root->right);
    cout << root->s << " ";
    return;
  }
  int main()
  {
    int n;
    while(cin >> n){
        TreeNode *root = NULL;
        for(int i = 0; i < n; i++){
            int t = 0; cin >> t;
            root = insert(root, t);
        }
        preorder(root); cout << endl;
        inorder(root); cout << endl;
        postorder(root); cout << endl;
  
    }
    return 0;
  }