Submission #293965

#	Time	Username	Problem	Language	Result	Execution time	Memory
293965		arayi	Sorting (IOI15_sorting)	C++17	36 / 100	2 ms	640 KiB

sorting

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

const int N = 2e5 + 30;

int n, m;
int a[N], ind[N], b[N], x[N], y[N];
int col[N];
void dfs(int v)
{
    col[v] = 1;
    if(!col[b[v]]) dfs(b[v]);
}
int cnt()
{
    int ret = 0;
    for (int i = 0; i < n; i++)
        if(!col[i]) ret++, dfs(i);
    for (int i = 0; i < n; i++) col[i] = 0;
    return n - ret;
}
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++) a[i] = S[i], ind[a[i]] = i;
    for (int i = 0; i < M; i++) x[i] = X[i], y[i] = Y[i];
    int l = 0, r = M, ans = M;
    while(l <= r)
    {
        int mid = (l + r) / 2;
        for (int i = 0; i < n; i++) b[i] = a[i];
        for (int i = 0; i < mid; i++) swap(b[x[i]], b[y[i]]);
        int sm = cnt();
        if(sm <= mid) ans = mid, r = mid - 1;
        else l = mid + 1;
    }
    m = ans;
    for (int i = 0; i < m; i++)
    {
        if(x[i] == y[i]) continue;
        col[x[i]]++, col[y[i]]++;
    }
    queue <int> q;
    for (int i = 0; i < n; i++)
    {
        if(!col[i]) q.push(i);
    }
    for (int i = 0; i < m; i++)
    {
        swap(a[x[i]], a[y[i]]);
        if(x[i] != y[i])
        {
            col[x[i]]--, col[y[i]]--;
            if(!col[x[i]]) q.push(x[i]);
            if(!col[y[i]]) q.push(y[i]);
            ind[a[x[i]]] = x[i];
            ind[a[y[i]]] = y[i];
        }
        while(!q.empty() && q.front() == a[q.front()]) q.pop();
        if(q.empty()) P[i] = Q[i] = 0;
        else
        {
            int i1 = q.front();
            //cout << i1 << endl;
            P[i] = i1;
            Q[i] = ind[i1];
            swap(a[P[i]], a[Q[i]]);
            ind[a[P[i]]] = P[i];
            ind[a[Q[i]]] = Q[i];
            q.pop();
        }
    }
    return m;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:23:76: warning: declaration of 'N' shadows a global declaration [-Wshadow]
   23 | int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[])
      |                                                                            ^
sorting.cpp:5:11: note: shadowed declaration is here
    5 | const int N = 2e5 + 30;
      |           ^

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