Submission #1073758

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073758		raduv	Xor Sort (eJOI20_xorsort)	C++17	100 / 100	6 ms	1240 KiB

xorsort

#include <bits/stdc++.h>
//#define DEBUG 1
using namespace std;
const int MAXN = 1'000;
const int MAXSUM = 100'000;
const int MAXBIT = 19;
int v[MAXN + 1];
vector<pair<int, int>> op;
signed main()
{

    int n, t, i, u, p, cn;
    scanf("%d%d", &n, &t);
    for( i = 1; i <= n; i++ ){
      scanf("%d", &v[i]);
    }
    if( t == 1 ){
      // select sort ca de ce nu? ( n <= 200 )
      for( u = n; u > 1; u-- ){
        p = 1;
        for( i = 1; i <= u; i++ ){
          if(v[p] < v[i])
            p = i;
        }
        for( i = 1; i < u; i++ )
          op.push_back({i, i + 1});
        for( i = p + 1; i <= u; i++ )
          op.push_back({i, i - 1});
        for( i = p - 2; i >= 1; i-- )
          op.push_back({i, i + 1});
        for( i = p; i < n; i++ )
          swap(v[i], v[i + 1]);
      }

      for( i = n; i >= 2; i-- )
        op.push_back({i - 1, i});

    }
    else{
      cn = n;
      for( p = MAXBIT; p >= 0; p-- ){
        for( i = 1; i < cn; i++ ){
          if(v[i] & (1 << p)){
            if( v[i + 1] & (1 << p)){
              op.push_back({i, i + 1});
              v[i] ^= v[i + 1];
            }
            else{
              op.push_back({i + 1, i});
              // au ambele bitul maxim (1 << p) acum
              op.push_back({i, i + 1});
              // iar acum nu mai are niciunul bitul (1 << p)
              v[i + 1] ^= v[i];
              v[i] ^= v[i + 1];
            }
          }
        }
        while( cn > 1 && (v[cn] & (1 << p)))
          cn--;
      }
    }
    printf("%d\n", (int)op.size());
    for( auto pi : op )
      printf("%d %d\n", pi.first, pi.second);
    #ifdef DEBUG
    for( i = 1; i <= n; i++ )
      printf("%d ", v[i]);
    #endif // DEBUG
    return 0;
}

Compilation message (stderr)

xorsort.cpp: In function 'int main()':
xorsort.cpp:13:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   13 |     scanf("%d%d", &n, &t);
      |     ~~~~~^~~~~~~~~~~~~~~~
xorsort.cpp:15:12: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |       scanf("%d", &v[i]);
      |       ~~~~~^~~~~~~~~~~~~

• Subtask 1: 25 / 25
• Subtask 2: 35 / 35
• Subtask 3: 40 / 40