제출 #804461

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
804461		rnl42	Colors (BOI20_colors)	C++14	0 / 100	2386 ms	208 KiB

Colors

#include <bits/stdc++.h>
using namespace std;
#define int long long

int N;
unordered_set<int> used;

bool isvalid(int cur) {
    int mini = 1, maxi = N-1;
    bool parity = false;
    while (mini <= maxi) {
        int mid = (mini+maxi)>>1;
        int next;
        if (!parity) {
            next = cur+mid;
        } else {
            next = cur-mid;
        }
        if (next < 0 || next >= N) return false;
        mini = mid+1;
        cur = next;
        parity ^= 1;
    }
    return true;
}

inline bool query(int x) {
    used.insert(x);
    cout << "? " << x+1 << '\n' << flush;
    assert(x >= 0 && x < N);
    bool ret;
    cin >> ret;
    return ret;
}

signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cin >> N;
    int mini = 1, maxi = N-1;
    int cur = max(N/3-10, 0ll);
    for (; !isvalid(cur); cur++);
    query(cur);
    bool parity = false;
    while (mini <= maxi) {
        int mid = (mini+maxi)>>1;
        int next;
        if (!parity) {
            next = cur+mid;
        } else {
            next = cur-mid;
        }
        if (query(next)) {
            maxi = mid;
        } else {
            mini = mid+1;
        }
        cur = next;
        parity ^= 1;
    }
    cout << "= " << mini << '\n';
}

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