Submission #804506

#	Time	Username	Problem	Language	Result	Execution time	Memory
804506		rnl42	Colors (BOI20_colors)	C++14	0 / 100	1 ms	464 KiB

Colors

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

int N;
unordered_set<int> used;

inline int getvalid(int N) {
    int mincur = 0, maxcur = 0;
    int cur = 0;
    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;
        }
        mini = mid+1;
        cur = next;
        parity ^= 1;
        mincur = min(mincur, cur);
        maxcur = max(maxcur, cur);
    }
    //assert(maxcur-mincur <= N-1);
    return -mincur;
}

inline bool query(int x) {
    assert(!used.count(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 cur = getvalid(N);
    int mini = 1, maxi = N-1;
    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 (used.count(next)) {
            int inter = max(0ll, N/3-10);
            for (; used.count(inter) || used.count(inter+mid); inter++);
            query(inter);
            next = inter+mid;
        }
        if (query(next)) {
            maxi = mid;
        } else {
            mini = mid+1;
        }
        cur = next;
        parity ^= 1;
    }
    cout << "= " << mini << '\n';
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 13
• Subtask 3: 0 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 33