Submission #669733

#	Time	Username	Problem	Language	Result	Execution time	Memory
669733		victor_gao	Sorting (IOI15_sorting)	C++17	100 / 100	445 ms	21800 KiB

sorting

#pragma GCC optimize("Ofast,unroll-loops")
#include "sorting.h"
#include <bits/stdc++.h>
#define MAXN 200015
using namespace std;
int bk[MAXN],pos_bk[MAXN],pre[MAXN],pos_pre[MAXN];
int solve(int N,int n,int S[],int P[],int Q[],int X[],int Y[]){
    int now=0,cnt_same=0;
    for (int i=0;i<N;i++){
        bk[i]=i; pos_bk[i]=i;
        pre[i]=S[i];  pos_pre[S[i]]=i;
        if (pre[i]==i) cnt_same++;
    }
    for (int i=n-1;i>=0;i--){
        swap(bk[X[i]],bk[Y[i]]);
        pos_bk[bk[X[i]]]=X[i];
        pos_bk[bk[Y[i]]]=Y[i];
    }
    for (int i=0;i<n;i++){
        if (cnt_same==N) return i;
        if (pre[X[i]]==X[i]) cnt_same--;
        if (pre[Y[i]]==Y[i]) cnt_same--;
        swap(pre[X[i]],pre[Y[i]]);
        if (pre[X[i]]==X[i]) cnt_same++;
        if (pre[Y[i]]==Y[i]) cnt_same++;
        pos_pre[pre[X[i]]]=X[i];
        pos_pre[pre[Y[i]]]=Y[i];
        swap(bk[X[i]],bk[Y[i]]);
        pos_bk[bk[X[i]]]=X[i];
        pos_bk[bk[Y[i]]]=Y[i];
        while (now<N&&pos_pre[now]==pos_bk[now])
            now++;
        if (now>=N){
            P[i]=0; Q[i]=0;
            continue;
        } 
        P[i]=pos_pre[now]; Q[i]=pos_bk[now];
        if (pre[P[i]]==P[i]) cnt_same--;
        if (pre[Q[i]]==Q[i]) cnt_same--;
        swap(pre[pos_pre[now]],pre[pos_bk[now]]);
        if (pre[P[i]]==P[i]) cnt_same++;
        if (pre[Q[i]]==Q[i]) cnt_same++;
        pos_pre[pre[pos_pre[now]]]=pos_pre[now];
        pos_pre[pre[pos_bk[now]]]=pos_bk[now];
    }
    if (cnt_same==N) return n;
    else return 1e9;
}
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
    int l=0,r=N+1;
    while (l<r){
        int mid=(l+r)>>1;
        if (solve(N,mid,S,P,Q,X,Y)<1e8) r=mid;
        else l=mid+1;
    }
    return solve(N,l,S,P,Q,X,Y);
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:49:39: warning: unused parameter 'M' [-Wunused-parameter]
   49 | 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: 18 / 18
• Subtask 5: 20 / 20
• Subtask 6: 26 / 26