Submission #259130

#	Time	Username	Problem	Language	Result	Execution time	Memory
259130		IOrtroiii	Sorting (IOI15_sorting)	C++14	0 / 100	1 ms	384 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[perm[i]];
         P[ans] = i;
         Q[ans++] = 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);
   iota(perm.begin(), perm.end(), 0);
   vector<int> invp = perm;
   for (int i = low - 1; i >= 0; --i) {
      P[i] = invp[P[i]];
      Q[i] = invp[Q[i]];
      swap(perm[X[i]], perm[Y[i]]);
      invp[perm[X[i]]] = X[i];
      invp[perm[Y[i]]] = Y[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: 0 / 8
• Subtask 2: 0 / 12
• Subtask 3: 0 / 16
• Subtask 4: 0 / 18
• Subtask 5: 0 / 20
• Subtask 6: 0 / 26