Submission #330258

#	Time	Username	Problem	Language	Result	Execution time	Memory
330258		mihai145	Sorting (IOI15_sorting)	C++14	100 / 100	410 ms	40236 KiB

sorting

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

const int NMAX = 2e5;
const int MMAX = 30 * NMAX;

int n, s[NMAX + 2], aux[NMAX + 2], inv[NMAX + 2];
int x[MMAX + 2], y[MMAX + 2];

bool vis[NMAX + 2];
std::vector <int> curr;
std::vector < std::vector <int> > cycles;

void dfs(int node)
{
    vis[node] = 1;
    curr.push_back(node);

    if(!vis[aux[node]])
        dfs(aux[node]);
}

bool Sorted(int limit)
{
    for(int i = 0; i < n; i++)
        aux[i] = s[i], vis[i] = 0;

    for(int i = 0; i < limit; i++)
        std::swap(aux[x[i]], aux[y[i]]);

    cycles.clear();
    for(int i = 0; i < n; i++)
        if(!vis[i])
        {
            curr.clear();
            dfs(i);
            cycles.push_back(curr);
        }

    int t = 0;
    for(auto it : cycles)
        t += ((int)it.size() - 1);

    return (t <= limit);
}

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[])
{
    n = N;
    for(int i = 0; i < n; i++)
    {
        s[i] = S[i];
    }
    for(int i = 0; i < M; i++)
    {
        x[i] = X[i];
        y[i] = Y[i];
    }

    int st = 0, dr = N, sol = -1;

    while(st <= dr)
    {
        int mid = (st + dr) >> 1;

        if(Sorted(mid))
        {
            sol = mid;
            dr = mid - 1;
        }
        else
        {
            st = mid + 1;
        }
    }

    ///to reconstruct the cycles
    Sorted(sol);

    std::vector < std::pair<int,int> > moves;
    for(auto it : cycles)
    {
        for(int i = 0; i < (int)it.size() - 1; i++)
        {
            moves.push_back({it[i], it[i + 1]});
        }
    }

    for(int i = 0; i < n; i++)
    {
        inv[s[i]] = i;
    }

    for(int i = 0; i < sol; i++)
    {
        int preX = s[X[i]];
        int preY = s[Y[i]];

        inv[preX] = Y[i];
        inv[preY] = X[i];

        std::swap(s[X[i]], s[Y[i]]);

        if(!moves.empty())
        {
            P[i] = inv[moves.back().first];
            Q[i] = inv[moves.back().second];
            moves.pop_back();
        }
        else
        {
            P[i] = Q[i] = 0;
        }
    }

    return sol;
}

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