Submission #259152

#	Time	Username	Problem	Language	Result	Execution time	Memory
259152		IOrtroiii	Sorting (IOI15_sorting)	C++14	100 / 100	207 ms	10184 KiB

sorting

#include "sorting.h"

#include <bits/stdc++.h>

using namespace std;

int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
   auto solve = [&](int mid) -> bool {
      vector<int> perm(N);
      for (int i = 0; i < N; ++i) {
         perm[i] = S[i];
      }
      for (int i = 0; i < mid; ++i) swap(perm[X[i]], perm[Y[i]]);
      vector<int> invp(N);
      for (int i = 0; i < N; ++i) invp[perm[i]] = i;
      int ans = 0;
      for (int i = 0; i < N; ++i) {
         if (perm[i] == i) continue;
         int j = invp[i];
         P[ans] = perm[i];
         Q[ans++] = perm[j];
         swap(perm[i], perm[j]);
         invp[perm[i]] = i;
         invp[perm[j]] = j;
      }
      for (int i = ans; i < mid; ++i) P[i] = Q[i] = 0;
      return ans <= mid;
   };
   int low = 0, high = N;
   while (low < high) {
      int mid = (low + high) >> 1;
      if (solve(mid)) high = mid;
      else low = mid + 1;
   }
   solve(low);
   vector<int> perm(N);
   for (int i = 0; i < N; ++i) perm[i] = S[i];
   vector<int> invp(N);
   for (int i = 0; i < N; ++i) invp[perm[i]] = i;
   for (int i = 0; i < low; ++i) {
      swap(perm[X[i]], perm[Y[i]]);
      invp[perm[X[i]]] = X[i];
      invp[perm[Y[i]]] = Y[i];
      P[i] = invp[P[i]];
      Q[i] = invp[Q[i]];
      swap(perm[P[i]], perm[Q[i]]);
      invp[perm[P[i]]] = P[i];
      invp[perm[Q[i]]] = Q[i];
   }
   return low;
}

Compilation message (stderr)

sorting.cpp: In function 'int findSwapPairs(int, int*, int, int*, int*, int*, int*)':
sorting.cpp:7:39: warning: unused parameter 'M' [-Wunused-parameter]
 int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
                                       ^

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