http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_8_A&lang=jp

Binary Search Tree I

#include <iostream>
#include<math.h>

using namespace std;


struct node {
    long value = 0;
    node *right = nullptr;
    node *left = nullptr;
};

struct tree {
    node *root = nullptr;
};


void insert(node *root, node *node1) {
    if (root->value > node1->value) {
        if (root->left == nullptr) {
            //cout << node1->value << " in" << endl;
            root->left = node1;
        } else {
            //cout << node1->value << " right" << endl;
            insert(root->left, node1);
        }
    } else {
        if (root->right == nullptr) {
            //cout << node1->value << " in" << endl;
            root->right = node1;
        } else {
            //cout << node1->value << " left" << endl;
            insert(root->right, node1);
        }
    }
}

void insert_tree(tree *tree1) {
    long in_key;
    cin >> in_key;

    node *node1 = (node *) malloc(sizeof(node));
    node1->value = in_key;
    if (tree1->root == nullptr) {
        tree1->root = node1;
    } else {
        insert(tree1->root, node1);
    }
}

void print_tree_mid(node *node1) {
    if(node1->left != nullptr)print_tree_mid(node1->left);
    cout << " " << node1->value;
    if(node1->right != nullptr)print_tree_mid(node1->right);
}

void print_tree_pre(node *node1) {
    cout << " " << node1->value;
    if(node1->left != nullptr)print_tree_pre(node1->left);
    if(node1->right != nullptr)print_tree_pre(node1->right);
}

void print_tree(tree *tree1){
    print_tree_mid(tree1->root);
    cout << endl;
    print_tree_pre(tree1->root);
    cout << endl;
}

int main() {
    long m;
    string PRINT = "print", INSERT = "insert", s;
    cin >> m;
    tree *tree1 = (struct tree *) malloc(sizeof(tree));
    for (int i = 0; i < m; i++) {
        cin >> s;
        if (s == INSERT) insert_tree(tree1);
        else print_tree(tree1);
    }
    return 0;
}