Submission #496705

#	Time	Username	Problem	Language	Result	Execution time	Memory
496705		kevin	Sorting (IOI15_sorting)	C++17	100 / 100	175 ms	21612 KiB

sorting

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

#define ll long long
#define vi vector<int>
#define all(x) x.begin(), x.end()
#define ca(v) for(auto i:v) cout<<i<<" ";
#define nl cout<<"\n"

const int MAXN = 5e5 + 5;

int findSwapPairs(int N, int* s, int M, int* X, int* Y, int* P, int* Q){
    int flg = 1;
    for(int i=0; i<N; i++) {
        if(s[i] != i) flg = 0;
    }
    if(flg) return 0;
    int l = 0;
    int r = M-1;
    int ans = M;
    vi S;
    for(int i=0; i<N; i++) S.push_back(s[i]);
    while(l <= r){
        int m = (l+r)/2;
        vi ar = S;
        for(int i=0; i<=m; i++){
            swap(ar[X[i]], ar[Y[i]]);
        }
        int cnt = 0;
        vi vis(N, 0);
        for(int i=0; i<N; i++) {
            if(vis[i]) continue;
            cnt++;
            int q = i;
            while(1){
                vis[q] = 1;
                if(vis[ar[q]]) break;
                q = ar[q];
            }
        }
        cnt = N - cnt;
        if(cnt-1 <= m){
            ans = m;
            r = m-1;
        }
        else l = m+1;
    }
    vi vis(N, 0);
    vi ar = S;
    for(int i=0; i<=ans; i++) swap(ar[X[i]], ar[Y[i]]);
    vi xm, ym;
    int cnt = 0;
    for(int i=0; i<N; i++) {
        if(vis[i]) continue;
        cnt++;
        int q = i;
        while(1){
            vis[q] = 1;
            if(vis[ar[q]]) break;
            xm.push_back(q);
            ym.push_back(ar[q]);
            q = ar[q];
        }
    }
    vector<int> pos(N);
    for(int i=0; i<N; i++) pos[S[i]] = i;
    reverse(xm.begin(), xm.end());
    reverse(ym.begin(), ym.end());
    for(int i=0; i<xm.size(); i++){
        swap(pos[S[X[i]]], pos[S[Y[i]]]);
        swap(S[X[i]], S[Y[i]]);
        P[i] = pos[xm[i]];
        Q[i] = pos[ym[i]];
    }
    return ans+1;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:69:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   69 |     for(int i=0; i<xm.size(); i++){
      |                  ~^~~~~~~~~~

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