#include <stdio.h>
#include <sys/time.h>
#include <sys/resource.h>

int compare(const void* xin, const void* yin)
{
int x,y;

x=(*((int*)xin));
y=(*((int*)yin));
return x-y;
}

double CPUtime()
{
  struct rusage rusage;
  getrusage(RUSAGE_SELF,&rusage);
  return rusage.ru_utime.tv_sec+rusage.ru_utime.tv_usec/1000000.0
    + rusage.ru_stime.tv_sec+rusage.ru_stime.tv_usec/1000000.0;
}

void duplicates_qsort(int seed,int n)
{
double startCPU;
int *table,i,duplicates;

table=(int*) malloc(n*sizeof(int));
if (table==NULL)
{
  printf("choked in duplicates_qsort()\n");
  exit(0);
}
srandom(seed);
for (i=0;i<n;i++)
  table[i]=abs(random());

startCPU=CPUtime();
qsort(table,n,sizeof(int),compare);

duplicates=0;
for (i=1;i<n;i++)
  if (table[i-1]==table[i])
    duplicates++;
printf("%d duplicates by qsort()\n",duplicates);
printf("CPU time for duplicates by qsort() %f\n",CPUtime()-startCPU);
}

main()
{
int seed,n;

printf("Enter seed: ");
fflush(stdout);
scanf("%d",&seed);
printf("Enter n: ");
fflush(stdout);
scanf("%d",&n);
duplicates_qsort(seed,n);
}