Submission #1054339

#	Time	Username	Problem	Language	Result	Execution time	Memory
1054339		vjudge1	Secret Permutation (RMI19_permutation)	C++17	100 / 100	1040 ms	600 KiB

permutation

#include "permutation.h"
#include<bits/stdc++.h>
using namespace std;
 
const int maxn = 300;
 
namespace {
	long long D[maxn];
	bool vis[maxn];
	vector<int> crr;
	vector<vector<int>> allans;
	mt19937 rng(123123);
}
 
bool bt(int pos, int n, const vector<int> &P){
	if(pos > n){
		if(abs(crr.back() - crr[0]) != D[1])return false;
		vector<int> nw(n);
		for(int i = 0; i < n; i++){
			nw[P[i]-1] = crr[i];
		}
		crr = nw;
		return true;
	}
	int tmp = crr.back() + D[pos]; 
	if(tmp <= n && !vis[tmp]){
		crr.push_back(tmp);
		vis[tmp] = 1;
		if(bt(pos+1, n, P))return true;
		vis[tmp] = 0;
		crr.pop_back();
	}
	
	tmp = crr.back() - D[pos]; 
	if(tmp > 0 && !vis[tmp]){
		crr.push_back(tmp);
		vis[tmp] = 1;
		if(bt(pos+1, n, P))return true;
		vis[tmp] = 0;
		crr.pop_back();
	}
	return false;
}
 
void solve(int N) {
	long long sum = 0;
	vector<int> P(N);
	iota(P.begin(), P.end(), 1);
	shuffle(P.begin(), P.end(), rng);
	for(int i = 1; i <= N; i++){
		D[i] = query(P);
		sum += D[i];
		P.push_back(P[0]);
		P.erase(P.begin());
	}
	sum /= N-1;
	for(int i = 1; i <= N; i++){
		D[i] = sum - D[i];
		// cout << D[i] << endl;
	}
	allans.clear();
 
	for(int i = 1; i <= N; i++){
		crr.push_back(i);
		vis[i] = 1;
		if(bt(2, N, P)){
			answer(crr);
			return;
		}
		vis[i] = 0;
		crr.pop_back();
	}
 
}

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