Code mẫu

#include <bits/stdc++.h>

using namespace std;

const int MAXN = 10000;

// fixed seed for debugging
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

// Irrelevant shit

int rnd(int n) {
    return uniform_int_distribution<int>(0, n - 1)(rng);
}

int compare(int i, int j) {
    cout << "compare " << i << " " << j << endl;
    char res; cin >> res;
    return res == '<';
}

int compare_k(int i) {
    cout << "compare_k " << i << endl;
    char res; cin >> res;
    return res == '<';
}

void answer(int i, int j) {
    cout << "answer " << i << " " << j << endl;
    exit(0);
}

void no_answer() {
    cout << "no_answer" << endl;
    exit(0);
}

int N;
int a[MAXN];

int main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL);

    cin >> N;
    iota(a, a+N, 1);
    shuffle(a, a+N, rng);

    int l = 0, r = N-1, answer_small = -1, answer_large = -1;
    while(l <= r) {
        int k = ((r - l) >> 1) + 1;
        nth_element(a+l, a+l+k-1, a+r+1, compare);

        if (compare_k(a[l + k - 1])) {
            answer_small = a[l + k - 1];
            l += k;
        } else {
            answer_large = a[l+k-1];
            r = l + k - 2;
        }
    }

    if (answer_small == -1 || answer_large == -1) {
        no_answer();
        return 0;
    }

    answer(answer_small, answer_large);

    return 0;
}