Cod sursa(job #824736)

Utilizator lucky1992Ion Ion lucky1992 Data 26 noiembrie 2012 21:37:36
Problema Statistici de ordine Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.35 kb
#include <cstdio>
#include <ctime>
#include <iostream>
#include <fstream>
#include <cstdlib>


using namespace std;




ifstream in("sdo.in");
ofstream out("sdo.out");


void swap( int&a, int&b ){
  int c = a;
  a = b;
  b = c;
}

int partition( int* A, int left, int right ){
  if( left == right )
    return left;
  int r = left +  rand()%( right - left );
  swap( A[r], A[right] );
  int x = A[right];
  int i = left - 1;
  for( int j = left; j <= right - 1; j++ ){
	if( A[j] < x ){
	  i++;
	  swap(A[i],A[j]);
	}
  }
  swap(A[i+1],A[right]);
  return i+1;
}

/*
 * recursive mode
 int GetKth( int* A, int left, int right, int k ){
    if( left == right ) return A[left];
    int q = partition( A, left, right );
    int i = q - left + 1;
    if( i == k )
      return A[q];
    else if ( k < i ) return GetKth( A, left, q-1, k );
    else return GetKth( A, q+1, right, k - i );
}
*/

int main( int argc, char* argv[] ){
   
    srand( (unsigned)time(NULL));
    int N = 0, k = 0;
    in >> N >> k;
    int* v = new int[N+1];
    
    for( int i = 1; i <= N; i++ )
      in >> v[i];
    in.close();
    int left = 1, right = N, q = 0;
    
    // iterative mode
    do{
      q = partition( v, left, right );
      if( k < q )
	right = q - 1;
      else if ( k > q )
	left = q + 1;
    }while( q != k );
    
    out << v[k]<<endl;
    out.close();
    delete []v;
    return 0;
}