Submission #1286822

#	Time	Username	Problem	Language	Result	Execution time	Memory
1286822		Faisal_Saqib	Sorting (IOI15_sorting)	C++20	100 / 100	137 ms	14932 KiB

sorting

#include "sorting.h"
// #include "grader.cpp"
#include <bits/stdc++.h>
using namespace std;
const int N=2e5+100;
int p[N],ind[N];
bool vis[N];
int findSwapPairs(int n, int s[], int m, int x[], int y[], int P[], int Q[]) {
	if(is_sorted(s,s+n))
		return 0;
int l=-1,r=m; // [0,m-1]
while(l+1<r)
{
	int mid=(l+r)/2;
	for(int i=0;i<n;i++)vis[i]=0,p[i]=s[i];
	for(int use=0;use<=mid;use++)
	{
		swap(p[x[use]],p[y[use]]);
	}
	bool post=1;
	int sz=0;
	for(int i=0;i<n;i++)
	{
		if(vis[i])continue;
		int j=i;
		vector<int> cyc;
		while(!vis[j])
		{
			cyc.push_back(j);
			vis[j]=1;
			j=p[j];
		}
		sz++;
	}
	sz=(n-sz);
	if(sz>(mid+1))
	{
		post=0;
	}
	if(post)
	{
		r=mid;
	}
	else
	{
		l=mid;
	}
}
int use=r;
for(int i=0;i<n;i++)p[i]=s[i],vis[i]=0,ind[s[i]]=i;
for(int i=0;i<=r;i++)
{
	swap(p[x[i]],p[y[i]]);
}
for(int i=0;i<n;i++)vis[i]=0;
vector<pair<int,int>> req;
for(int i=0;i<n;i++)
{
	if(vis[i])continue;
	int j=i;
	vector<int> cyc;
	while(!vis[j])
	{
		cyc.push_back(j);
		vis[j]=1;
		j=p[j];
	}
	for(int i=1;i<cyc.size();i++)
	{
		req.push_back({p[cyc[i-1]],p[cyc[i]]});
	}
}
for(int i=0;i<n;i++)p[i]=s[i],ind[s[i]]=i;
for(int i=0;i<m;i++)P[i]=0,Q[i]=0;
// if(req.size()>m)
// {
// 	return 0;
// }
for(int i=0;i<req.size();i++)
{
	swap(ind[p[x[i]]],ind[p[y[i]]]);
	swap(p[x[i]],p[y[i]]);
	P[i]=ind[req[i].first],Q[i]=ind[req[i].second];
	swap(ind[p[P[i]]],ind[p[Q[i]]]);
	swap(p[P[i]],p[Q[i]]); 
	// swap()
}
for(int i=req.size();i<=use;i++)
{
	swap(ind[p[x[i]]],ind[p[y[i]]]);
	swap(p[x[i]],p[y[i]]);
}
return use+1;
return m;
}

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