Submission #722289

#	Time	Username	Problem	Language	Result	Execution time	Memory
722289		tvladm2009	Secret Permutation (RMI19_permutation)	C++17	100 / 100	1859 ms	332 KiB

permutation

#include <bits/stdc++.h>
#include "permutation.h"

using namespace std;

typedef long long ll;

const int N_MAX = 256;

///mt19937 rnd(time(0));

vector <int> sol, questions;
bool used[N_MAX + 2];

bool found = 0;

void dfs(int pos, int N) {
    if (pos == N - 1) {
        if (abs(sol[0] - sol[pos]) == questions[pos]) {
            found = 1;
        }
        return;
    }
    int next = sol[pos] - questions[pos];
    if (1 <= next && next <= N && !used[next]) {
        sol.push_back(next);
        used[next] = 1;
        dfs(pos + 1, N);
        if (found == 1) {
            return;
        }
        used[next] = 0;
        sol.pop_back();
    }
    next = sol[pos] + questions[pos];
    if (1 <= next && next <= N && !used[next]) {
        sol.push_back(next);
        used[next] = 1;
        dfs(pos + 1, N);
        if (found == 1) {
            return;
        }
        used[next] = 0;
        sol.pop_back();
    }
}

void solve(int N) {
    vector <int> V;
    for (int i = 1; i <= N; i++) {
        V.push_back(i);
    }
    srand(257);
    random_shuffle(V.begin(), V.end());
    vector <int> C = V;
    questions.clear();
    for (int i = 1; i <= N; i++) {
        rotate(V.begin(), V.begin() + 1, V.end());
        questions.push_back(query(V));
    }
    int sum = 0;
    for (int it : questions) {
        sum += it;
    }
    sum /= N - 1;
    for (int &it : questions) {
        it = sum - it;
    }
    for (int i = 1; i <= N; i++) {
        for (int j = 1; j <= N; j++) {
            used[j] = 0;
        }
        sol.clear();
        sol.push_back(i);
        used[i] = 1;
        found = 0;
        dfs(0, N);
        if (found == 1) {
            vector <int> ret(N);
            for (int j = 0; j < N; j++) {
                ret[C[j] - 1] = sol[j];
            }
            answer(ret);
            return;
        }
    }
}

Compilation message (stderr)

stub.cpp: In function 'int query(int*)':
stub.cpp:15:9: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |   fscanf(stdin, "%d", &x);
      |   ~~~~~~^~~~~~~~~~~~~~~~~
stub.cpp: In function 'int main(int, char**)':
stub.cpp:48:9: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |   fscanf(stdin, "%d", &N);
      |   ~~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 35 / 35
• Subtask 3: 50 / 50