demo_binary_search_tree_1.cpp

#include <cstdio>
#include <cstdlib>
#include <string>
#include <iostream>
using namespace std;

struct Node {
    int key;
    Node *right, *left, *parent;
};

Node *root, *NIL;

void insert(int k ) {

    Node *y = NIL;
    Node *x = root;
    Node *z;

    z = (Node *)malloc(sizeof(Node));
    z->key = k;
    z->left = NIL;
    z->right = NIL;

    while (x != NIL) {
        y = x;
        if (z->key < x->key) {
            x = x->left;
        } else {
            x = x->right;
        }
    }

    z->parent = y;
    if (y == NIL) {
        root = z;
    } else {
        if (z->key < y->key) {
            y->left = z;
        } else {
            y->right = z;
        }
    }
}

void inorder(Node *u) {

    if (u == NIL) return;
    inorder(u->left);
    printf(" %d", u->key);
    inorder(u->right);
}

void preorder(Node *u) {

    if (u == NIL) return;
    printf(" %d", u->key);
    preorder(u->left);
    preorder(u->right);
}

int main () {

    int n, i, x;
    string com;

    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        cin >> com;
        if (com == "insert") {
            scanf("%d", &x);
            insert(x);
        } else if (com == "print") {
            inorder(root);
            printf("\n");
            preorder(root);
            printf("\n");
        }
    }

    return 0;
}