Submission #68017

#	Time	Username	Problem	Language	Result	Execution time	Memory
68017		MKopchev	Sorting (IOI15_sorting)	C++14	36 / 100	6 ms	668 KiB

sorting

#include<bits/stdc++.h>
#include "sorting.h"
using namespace std;
const int nmax=2e5+42;
int arr[nmax];
bool been[nmax];
vector< pair<int,int> > change;
int findSwapPairs(int N,int S[],int M,int X[],int Y[],int P[],int Q[])
{
    int ok=N,not_ok=-1;
    while(ok-not_ok>1)
    {
        int av=(ok+not_ok)/2;
        //test av
        for(int j=0;j<N;j++)
            arr[j]=S[j];

        for(int j=0;j<av;j++)
            swap(arr[X[j]],arr[Y[j]]);

        memset(been,0,sizeof(been));
        int now=0;
        for(int i=0;i<N;i++)
            if(been[i]==0)
            {
                int j=i,d=0;
                while(been[j]==0)
                {
                    been[j]=1;
                    d++;
                    j=arr[j];
                }
                now=now+d-1;
            }
        //cout<<av<<" -> "<<now<<endl;
        if(now<=av)ok=av;
        else not_ok=av;
    }
    for(int j=0;j<N;j++)
        arr[j]=S[j];
    for(int j=0;j<ok;j++)
        swap(arr[X[j]],arr[Y[j]]);

    memset(been,0,sizeof(been));
    int now=0;
    for(int i=0;i<N;i++)
        if(been[i]==0)
        {
            int j=i,d=0;
            while(been[j]==0)
            {
                been[j]=1;
                d++;
                j=arr[j];
                if(i!=j)change.push_back({min(i,j),max(i,j)});
            }

        }

    //reverse(change.begin(),change.end());

    for(int i=0;i<ok;i++)
    {
        pair<int,int> now=change[i];
        for(int j=ok-1;j>i;j--)
        {
            int a=-1,b=-1,q=-1;
            if(X[j]==now.first)a=X[j],b=Y[j],q=now.second;
            else if(Y[j]==now.first)a=Y[j],b=X[j],q=now.second;
            else if(X[j]==now.second)a=X[j],b=Y[j],q=now.first;
            else if(Y[j]==now.second)a=Y[j],b=X[j],q=now.first;
            if(a!=-1)now={b,q};
            //cout<<"after "<<j<<" step, "<<now.first<<" "<<now.second<<endl;
        }
        P[i]=now.first;
        Q[i]=now.second;
        //cout<<i<<" -> "<<now.first<<" "<<now.second<<endl;
    }
    //test
    for(int j=0;j<N;j++)
        arr[j]=S[j];
    for(int i=0;i<ok;i++)
    {
        swap(arr[X[i]],arr[Y[i]]);
        swap(arr[P[i]],arr[Q[i]]);
        //for(int j=0;j<N;j++)cout<<arr[j]<<" ";cout<<endl;
    }

    for(int i=0;i<N;i++)
        if(arr[i]!=i)return -1;

    return ok;
}
/*
int n=5;
int S[5]={4,3,2,1,0};
int m=6;
int X[6]={0,1,2,3,0,1};
int Y[6]={1,2,3,4,1,2};
int P[6];
int Q[6];
int main()
{
    cout<<findSwapPairs(n,S,m,X,Y,P,Q)<<endl;
}
*/

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:64:23: warning: declaration of 'now' shadows a previous local [-Wshadow]
         pair<int,int> now=change[i];
                       ^~~
sorting.cpp:45:9: note: shadowed declaration is here
     int now=0;
         ^~~
sorting.cpp:45:9: warning: unused variable 'now' [-Wunused-variable]
sorting.cpp:8:37: warning: unused parameter 'M' [-Wunused-parameter]
 int findSwapPairs(int N,int S[],int M,int X[],int Y[],int P[],int Q[])
                                     ^

• Subtask 1: 8 / 8
• Subtask 2: 12 / 12
• Subtask 3: 16 / 16
• Subtask 4: 0 / 18
• Subtask 5: 0 / 20
• Subtask 6: 0 / 26