Submission #464091

#	Time	Username	Problem	Language	Result	Execution time	Memory
464091		amunduzbaev	Xor Sort (eJOI20_xorsort)	C++14	100 / 100	10 ms	1124 KiB

xorsort

#include "bits/stdc++.h"
using namespace std;
#define ar array

vector<ar<int, 2>> get(vector<int>& a, int b = 20){
	if(a.empty()) return {};
	vector<int> tmp;
	for(auto x : a) tmp.push_back(x>>b&1);
	
	vector<ar<int, 2>> rr;
	
	for(int i=0;i+1<(int)tmp.size();i++){
		if(tmp[i] && tmp[i+1]){
			tmp[i] ^= 1;
			rr.push_back({i, i+1});
			a[i] ^= a[i+1];
		} else if(tmp[i] && tmp[i+1] == 0){
			swap(tmp[i], tmp[i+1]);
			rr.push_back({i+1, i});
			rr.push_back({i, i+1});
			a[i+1] ^= a[i];
			a[i] ^= a[i+1];
		}
	}
	
	if(b){
		if(tmp.back()) a.pop_back();
		vector<ar<int, 2>> tt = get(a, b - 1);
		rr.insert(rr.end(), tt.begin(), tt.end());
	}
	
	return rr;
}

void solve(){
	int s, n; cin>>n>>s;
	vector<int> a(n);
	for(auto& x : a) cin>>x;
	if(s == 1){
		vector<array<int, 2>> mx, rr;
		for(int i=0;i<n;i++){
			mx.push_back({a[i], i});
		} sort(mx.rbegin(), mx.rend());
		
		for(int i=0;i<(int)mx.size();i++){
			int p = mx[i][1];
			
			for(int i=0;i+1<n;i++){
				a[i] ^= a[i+1];
				rr.push_back({i, i+1});
			}
			
			if(i) n--;
			
			for(int i=p;i+1<n;i++){
				a[i+1] ^= a[i];
				rr.push_back({i+1, i});
			}
			
			for(int i=p-2;i>=0;i--){
				a[i] ^= a[i+1];
				rr.push_back({i, i+1});
			}
			
			assert(a[n - 1] == mx[i][0]);
			for(int j=i + 1;j<(int)mx.size();j++){
				if(mx[j][1] > p) mx[j][1]--;
			}
			//~ for(int i=0;i<(int)a.size();i++) cout<<a[i]<<" ";
			//~ cout<<"\n";
		}
		
		cout<<(int)rr.size()<<"\n";
		for(auto x : rr) cout<<x[0] + 1<<" "<<x[1] + 1<<"\n";
	} else {
		vector<ar<int, 2>> res = get(a);
		cout<<(int)res.size()<<"\n";
		for(auto x : res) cout<<x[0] + 1<<" "<<x[1] + 1<<"\n";
		cout<<"\n";
	}
}

/*

5 1
3 2 8 4 1

*/

signed main(){
	ios_base::sync_with_stdio(0); cin.tie(0);
	int t = 1;
	//~ cin>>t;
	while(t--) solve();
}

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