Submission #1287383

#	Time	Username	Problem	Language	Result	Execution time	Memory
1287383		WH8	Sorting (IOI15_sorting)	C++20	100 / 100	96 ms	14616 KiB

sorting

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

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
    int l=-1,r=M;
    for(int i=0;i<M;i++)P[i]=Q[i]=0;
    while(l<r-1){
		int mid=(l+r)/2;
		vector<bool> vis(N, 0);
		vector<int> cur(N); 
		for(int i=0;i<N;i++)cur[i]=S[i];
		for(int i=0;i<mid;i++){
			swap(cur[X[i]], cur[Y[i]]);
		}
		int cycles=0;
		for(int i=0;i<N;i++){
			if(!vis[i]){
				cycles++;
				int c=i;
				while(true){
					vis[c]=true;
					if(vis[cur[c]])break;
					c=cur[c];
				}
			}
		}
		if(N-cycles <= mid){
			r=mid;
		}
		else l=mid;
	}
	vector<bool> vis(N, 0);
	vector<int> cur(N); 
	for(int i=0;i<N;i++)cur[i]=S[i];
	for(int i=0;i<r;i++){
		swap(cur[X[i]], cur[Y[i]]);
	}
	vector<pair<int,int>> todo;
	for(int i=0;i<N;i++){
		if(!vis[i]){
			int c=i;
			vis[i]=true;
			while(true){
				vis[c]=true;
				if(vis[cur[c]])break;
				
				todo.push_back({c, cur[c]});
				c=cur[c];
			}
		}
	}
	vector<int> pos(N);
	for(int i=0;i<N;i++){
		cur[i]=S[i];
		pos[cur[i]]=i;
	}

	for(int i=0;i<(int)(todo.size());i++){
		//~ printf("trying to swap values %d with %d\n", todo[i].first, todo[i].second);
		pos[cur[X[i]]]=Y[i];
		pos[cur[Y[i]]]=X[i];
		swap(cur[X[i]], cur[Y[i]]);
		//~ for(int j=0;j<N;j++){
			//~ cout<<cur[j]<<" ";
		//~ }
		//~ cout<<endl;
		P[i]=pos[todo[i].first];
		Q[i]=pos[todo[i].second];
		swap(cur[pos[todo[i].first]], cur[pos[todo[i].second]]);
		swap(pos[todo[i].first], pos[todo[i].second]);
		//~ for(int j=0;j<N;j++){
			//~ cout<<cur[j]<<" ";
		//~ }
		//~ cout<<endl;
	}
	return r;
}

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 18 / 18
• Subtask 5: 20 / 20
• Subtask 6: 26 / 26