binary search tree

struct bst {
    struct node {
        int k;
        node *l, *r;
        node(int x = 0): k(x), l(nullptr), r(nullptr) {}
    }*root;

//constructor
    bst(): root(nullptr) {}

//insert
    void _insert(int x, node* cur) {
        //border
        if (!root) {root = new node(x); return;}

        //common
        if (x < cur->k) {
            //go left
            if (cur->l) _insert(x, cur->l);
            else cur->l = new node(x);
        } else {
            if (cur->r) _insert(x, cur->r);
            else cur->r = new node(x);
        }
    }
    void insert(int x) {
        _insert(x, root);
    }

//print
    void _print(node* cur) {
        if (!cur) return;
        _print(cur->l);
        cout << cur->k << ' ';
        _print(cur->r);
    }
    void print() {
        _print(root);
    }
};

inline void solve() {
    bst tree;
    for (auto && i : {1, 5, 4, 2, 0, 3, 6, 9, 7, 8})
        tree.insert(i);
    tree.print();
}