Submission #590907

#	Time	Username	Problem	Language	Result	Execution time	Memory
590907		AlperenT	Sorting (IOI15_sorting)	C++17	100 / 100	161 ms	11636 KiB

sorting

#include <bits/stdc++.h>
#include "sorting.h"

using namespace std;

int swapcnt(vector<int> v){
    int cnt = 0, n = v.size();

    vector<bool> vis(n, false);

    for(int i = 0; i < n; i++){
        if(!vis[i]){
            int x = i;

            while(!vis[x]){
                cnt++;

                vis[x] = true;
                x = v[x];
            }

            cnt--;
        }
    }

    return cnt;
}

int findSwapPairs(int n, int S[], int M, int X[], int Y[], int P[], int Q[]){
    vector<int> v, v2;

    v.assign(n, 0);

    copy(S, S + n, v.begin());

    int l = -1, r = M;

    while(r - l > 1){
        int m = l + (r - l) / 2;

        v2 = v;

        for(int i = 0; i < m; i++) swap(v2[X[i]], v2[Y[i]]);

        if(swapcnt(v2) <= m) r = m;
        else l = m;
    }   

    v2 = v;

    for(int i = 0; i < r; i++) swap(v2[X[i]], v2[Y[i]]);

    vector<pair<int, int>> swaps;

    vector<bool> vis(n, false);

    for(int i = 0; i < n; i++){
        if(!vis[i]){
            vis[i] = true;

            int x = i;

            while(!vis[v2[x]]){
                vis[x] = true;

                swaps.push_back({v2[x], v2[v2[x]]});

                x = v2[x];
            }
        }
    }

    while(swaps.size() < r) swaps.push_back({0, 0});

    vector<int> where(n);

    for(int i = 0; i < n; i++) where[v[i]] = i;

    for(int i = 0; i < r; i++){
        swap(where[v[X[i]]], where[v[Y[i]]]);
        swap(v[X[i]], v[Y[i]]);

        P[i] = where[swaps[i].first];
        Q[i] = where[swaps[i].second];

        swap(where[v[P[i]]], where[v[Q[i]]]);
        swap(v[P[i]], v[Q[i]]);
    }

    assert(is_sorted(v.begin(), v.end()));

    return r;
}

Compilation message (stderr)

sorting.cpp: In function 'int swapcnt(std::vector<int>)':
sorting.cpp:7:28: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
    7 |     int cnt = 0, n = v.size();
      |                      ~~~~~~^~
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:73:24: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   73 |     while(swaps.size() < r) swaps.push_back({0, 0});
      |           ~~~~~~~~~~~~~^~~

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