Submission #544229

#	Time	Username	Problem	Language	Result	Execution time	Memory
544229		timreizin	Sorting (IOI15_sorting)	C++17	0 / 100	1 ms	468 KiB

sorting

#include "sorting.h"
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

bool check(int m, vector<int> s, vector<pair<int, int>> &swaps)
{
    for_each(swaps.begin(), swaps.begin() + m, [&s](auto i){ swap(s[i.first], s[i.second]); });
    int res = 0;
    for (int i = 0; i < s.size(); ++i)
    {
        if (s[i] == i) continue;
        ++res;
        swap(s[i], s[s[i]]);
    }
    return res <= m;
}

int findSwapPairs(int n, int S[], int m, int X[], int Y[], int P[], int Q[])
{
    vector<int> s(n);
    for (int i = 0; i < n; ++i) s[i] = S[i];
    vector<pair<int, int>> swaps(m);
    for (int i = 0; i < m; ++i)
    {
        swaps[i].first = X[i];
        swaps[i].second = Y[i];
    }
    int l = 0, r = m;
    while (l < r)
    {
        int m = (l + r) >> 1;
        if (check(m, s, swaps)) r = m;
        else l = m + 1;
    }
    //l - res
    //cout << l;
    vector<int> finish = s;
    for_each(swaps.begin(), swaps.begin() + l, [&s = finish](auto i){ swap(s[i.first], s[i.second]); });
    vector<int> pos(n);
    for (int i = 0; i < n; ++i) pos[s[i]] = i;
    for (int i = 0, j = 0; j < l; ++i)
    {
        if (i == n)
        {
            P[l - 1] = 0;
            Q[l - 1] = 0;
            break;
        }
        //if in the end and j != l add (0, 0)
        if (finish[i] == i) continue;
        swap(pos[s[swaps[j].first]], pos[s[swaps[j].second]]);
        swap(s[swaps[j].first], s[swaps[j].second]);
        //a = finish[i], b = finish[finish[i]]
        int a = finish[i];
        int b = finish[a];
        swap(finish[i], finish[a]);
        P[j] = pos[a];
        Q[j] = pos[b];
        swap(s[pos[a]], s[pos[b]]);
        swap(pos[a], pos[b]);
        ++j;
    }
	return l;
}

Compilation message (stderr)

sorting.cpp: In function 'bool check(int, std::vector<int>, std::vector<std::pair<int, int> >&)':
sorting.cpp:12:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |     for (int i = 0; i < s.size(); ++i)
      |                     ~~^~~~~~~~~~
sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:34:13: warning: declaration of 'int m' shadows a parameter [-Wshadow]
   34 |         int m = (l + r) >> 1;
      |             ^
sorting.cpp:21:39: note: shadowed declaration is here
   21 | int findSwapPairs(int n, int S[], int m, int X[], int Y[], int P[], int Q[])
      |                                   ~~~~^

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