题解 | #二叉排序树# 还真是二叉链表

#include <iostream>
using namespace std;

typedef struct Treenode {
    struct Treenode* left;
    struct Treenode* right;
    int val;
}*Tree;

void insert(Tree &root, int x) {
    if (!root) {
        root = (Treenode*) malloc(sizeof(Treenode));
        root->left = nullptr;
        root->right = nullptr;
        root->val = x;
        return;
    } 
    if (root->val==x) return;
    else if (root->val > x) insert(root->left, x);
    else insert(root->right, x);
}

void preorder(Tree& root) {
    if (root) {
        cout << root->val << " ";
        preorder(root->left);
        preorder(root->right);
    }
}

void inorder(Tree&  root) {
    if (root) {
        inorder(root->left);
        cout << root->val << " ";
        inorder(root->right);
    }
}

void postorder(Tree&  root) {
    if (root) {
        postorder(root->left);
        postorder(root->right);
        cout << root->val << " ";
    }
}

int main() {
    int n;
    while (cin >> n) {
        int x;
        Treenode* root = nullptr;
        while (n--) {
            cin >> x;
            insert(root, x);
        }
        preorder(root);
        cout<<endl;
        inorder(root);
        cout<<endl;
        postorder(root);
        cout<<endl;
        free(root);
    }
}