Submission #285115

#	Time	Username	Problem	Language	Result	Execution time	Memory
285115		SamAnd	Sorting (IOI15_sorting)	C++17	100 / 100	515 ms	30344 KiB

sorting

#include "sorting.h"
#include <bits/stdc++.h>
using namespace std;
#define m_p make_pair
#define fi first
#define se second
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
const int N = 200005 * 3;

int n, m;
int S[N];
int X[N], Y[N];

int a[N];
int b[N], bb[N];

int uu[N];

int u[N];

bool c[N];

int P[N], Q[N];
bool stg(int q)
{
    for (int i = 0; i < n; ++i)
    {
        a[i] = S[i];
        b[i] = i;
        bb[i] = i;
        c[i] = false;
    }
    for (int i = 0; i < q; ++i)
    {
        swap(b[bb[X[i]]], b[bb[Y[i]]]);
        swap(bb[X[i]], bb[Y[i]]);
    }
    for (int i = 0; i < n; ++i)
    {
        uu[b[i]] = i;
    }
    for (int i = 0; i < n; ++i)
    {
        u[i] = uu[a[i]];
    }

    for (int i = 0; i < n; ++i)
    {
        b[i] = i;
        bb[i] = i;
    }

    int ans = 0;
    for (int i = 0; i < n; ++i)
    {
        int x = i;
        if (c[x])
            continue;
        vector<int> v;
        c[x] = true;
        while (1)
        {
            x = u[x];
            if (c[x])
                break;
            v.push_back(x);
            c[x] = true;
        }

        for (int j = 0; j < sz(v); ++j)
        {
            swap(b[bb[X[ans]]], b[bb[Y[ans]]]);
            swap(bb[X[ans]], bb[Y[ans]]);

            swap(a[i], a[v[j]]);
            P[ans] = b[i];
            Q[ans] = b[v[j]];
            ans++;
        }
    }
    while (ans < q)
    {
        P[ans] = 0;
        Q[ans] = 0;
        ans++;
    }

    return ans <= q;
}

int findSwapPairs(int N_, int S[], int M_, int X[], int Y[], int P[], int Q[])
{
    n = N_;
    m = M_;

    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 l = 0, r = m;
    int ans = -1;
    while (l <= r)
    {
        int mid = (l + r) / 2;
        if (stg(mid))
        {
            ans = mid;
            r = mid - 1;
        }
        else
            l = mid + 1;
    }

    assert(ans != -1);

    stg(ans);

    for (int i = 0; i < ans; ++i)
    {
        P[i] = ::P[i];
        Q[i] = ::Q[i];
    }

    for (int i = 0; i < ans; ++i)
    {
        swap(S[X[i]], S[Y[i]]);
        swap(S[P[i]], S[Q[i]]);
    }

    for (int i = 0; i < n; ++i)
    {
        if (S[i] != i)
        {
            assert(false);
        }
    }

    return ans;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:92:78: warning: declaration of 'Q' shadows a global declaration [-Wshadow]
   92 | int findSwapPairs(int N_, int S[], int M_, int X[], int Y[], int P[], int Q[])
      |                                                                              ^
sorting.cpp:24:11: note: shadowed declaration is here
   24 | int P[N], Q[N];
      |           ^
sorting.cpp:92:78: warning: declaration of 'P' shadows a global declaration [-Wshadow]
   92 | int findSwapPairs(int N_, int S[], int M_, int X[], int Y[], int P[], int Q[])
      |                                                                              ^
sorting.cpp:24:5: note: shadowed declaration is here
   24 | int P[N], Q[N];
      |     ^
sorting.cpp:92:78: warning: declaration of 'Y' shadows a global declaration [-Wshadow]
   92 | int findSwapPairs(int N_, int S[], int M_, int X[], int Y[], int P[], int Q[])
      |                                                                              ^
sorting.cpp:13:11: note: shadowed declaration is here
   13 | int X[N], Y[N];
      |           ^
sorting.cpp:92:78: warning: declaration of 'X' shadows a global declaration [-Wshadow]
   92 | int findSwapPairs(int N_, int S[], int M_, int X[], int Y[], int P[], int Q[])
      |                                                                              ^
sorting.cpp:13:5: note: shadowed declaration is here
   13 | int X[N], Y[N];
      |     ^
sorting.cpp:92:78: warning: declaration of 'S' shadows a global declaration [-Wshadow]
   92 | int findSwapPairs(int N_, int S[], int M_, int X[], int Y[], int P[], int Q[])
      |                                                                              ^
sorting.cpp:12:5: note: shadowed declaration is here
   12 | int S[N];
      |     ^

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