Submission #775100

#	Time	Username	Problem	Language	Result	Execution time	Memory
775100		daoquanglinh2007	Xor Sort (eJOI20_xorsort)	C++17	65 / 100	7 ms	1236 KiB

xorsort

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

#define pii pair <int, int>
#define fi first
#define se second
#define mp make_pair
#define getbit(x, i) ((x&(1<<i)) != 0)

const int NM = 1000;

int N, S, a[NM+5], idx[NM+5];
vector <pii> ans;

void op(int i, int j){
	ans.push_back(mp(i, j));
	a[i] ^= a[j];
}

void swaping(int i){
	op(i+1, i);
	op(i, i+1);
	op(i+1, i);
}

bool cmp(int x, int y){
	int i = min(x, N-x+1), j = min(y, N-y+1);
	if (i != j) return i < j;
	return x < y;
}

void solve1(){
	for (int i = 1; i <= N; i++)
		idx[i] = i;
	sort(idx+1, idx+1+N, cmp);
	for (int ii = 1; ii <= N; ii++){
		int i = idx[ii];
		int k = i;
		if (ii%2 != 0){
			for (int j = i+1; j <= N; j++)
				if (a[j] < a[k]) k = j;
			for (int j = k-1; j >= i; j--)
				swaping(j);
		}
		else{
			for (int j = 1; j < i; j++)
				if (a[j] > a[k]) k = j;
			for (int j = k+1; j <= i; j++)
				swaping(j-1);
		}
	}
}

void solve2(){
	int tar = N+1;
	for (int i = 19; i >= 0; i--){
		bool ok = 0;
		for (int j = 1; j <= N; j++)
			if (getbit(a[j], i)){
				ok = 1;
				break;
			}
		if (ok == 0) continue;
		tar--;
		for (int j = 1; j < tar; j++)
			if (getbit(a[j], i) && !getbit(a[j+1], i)){
				op(j+1, j);
				op(j, j+1);
			}
			else if (getbit(a[j], i) && getbit(a[j+1], i)){
				op(j, j+1);
			}
	}
}

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin >> N >> S;
	for (int i = 1; i <= N; i++) cin >> a[i];
	if (S == 1) solve1();
	else solve2();
	cout << ans.size() << '\n';
	for (int i = 0; i < ans.size(); i++)
		cout << ans[i].fi << ' ' << ans[i].se << '\n';
	return 0;
}

Compilation message (stderr)

xorsort.cpp: In function 'int main()':
xorsort.cpp:85:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |  for (int i = 0; i < ans.size(); i++)
      |                  ~~^~~~~~~~~~~~

• Subtask 1: 25 / 25
• Subtask 2: 0 / 35
• Subtask 3: 40 / 40