Cod sursa(job #379986)

Utilizator mlazariLazari Mihai mlazari Data 4 ianuarie 2010 16:15:37
Problema Statistici de ordine Scor 60
Compilator cpp Status done
Runda Arhiva educationala Marime 0.82 kb
#include<stdio.h>
#include<time.h>
#include<stdlib.h>


#define NMAX 3000003

int n,k,i,j,l,r,sol,m[NMAX],*it,*jt;
bool d;

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

int randPiv(int l,int r) {
  return l+rand()%(r-l+1);
}

int main() {
  freopen("sdo.in","r",stdin);
  freopen("sdo.out","w",stdout);
  scanf("%d%d",&n,&k);
  for(i=1;i<=n;i++) scanf("%d",m+i);
  l=1;
  r=n;
  do {
    i=l;
    j=r;
    it=m+l;
    jt=m+r;
    swap(m[i],m[randPiv(l,r)]);
    d=false;
    while(i<j) {
      if(*it>*jt) {
        swap(*it,*jt);
        d=!d;
      }
      if(d) {
        ++i;
        ++it;
      }
      else {
        --j;
        --jt;
      }
    }
    if(i==k) sol=*it;
    else
     if(k<i) r=i-1;
     else l=i+1;
  } while(!sol);
  printf("%d\n",sol);
  return 0;
}