Submission #433061

#	Time	Username	Problem	Language	Result	Execution time	Memory
433061		timmyfeng	Sorting (IOI15_sorting)	C++17	100 / 100	332 ms	15192 KiB

sorting

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

#include "sorting.h"

const int N = 200000;

int perm[N], inv[N], first[N], second[N];
bool visited[N];

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
    int low = 0, high = M + 1;
    while (low < high) {
        int mid = (low + high) / 2;

        copy(S, S + N, perm);
        for (int i = 0; i < mid; ++i) {
            swap(perm[X[i]], perm[Y[i]]);
        }

        int count = 0;
        fill(visited, visited + N, false);
        fill(first, first + N, 0);
        fill(second, second + N, 0);
        for (int i = 0; i < N; ++i) {
            while (perm[i] != i) {
                first[count] = perm[i], second[count] = perm[perm[i]], ++count;
                swap(perm[i], perm[perm[i]]);
            }
        }

        if (count <= mid) {
            high = mid;

            copy(S, S + N, perm);
            for (int i = 0; i < N; ++i) {
                inv[perm[i]] = i;
            }

            for (int i = 0; i < mid; ++i) {
                swap(perm[X[i]], perm[Y[i]]);
                swap(inv[perm[X[i]]], inv[perm[Y[i]]]);
                P[i] = first[i], Q[i] = second[i];
                swap(inv[P[i]], inv[Q[i]]);
                P[i] = inv[P[i]], Q[i] = inv[Q[i]];
                swap(perm[P[i]], perm[Q[i]]);
            }
        } else {
            low = mid + 1;
        }
    }
    return low;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:11:23: warning: declaration of 'N' shadows a global declaration [-Wshadow]
   11 | int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
      |                   ~~~~^
sorting.cpp:6:11: note: shadowed declaration is here
    6 | const int N = 200000;
      |           ^

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