```// -*- mode: c++ -*-
// \$Id: heapsort.g++,v 1.4 2001/06/20 03:20:02 doug Exp \$
// http://www.bagley.org/~doug/shootout/

#include <iostream>
#include <stdlib.h>
#include <math.h>

using namespace std;

#define IM 139968
#define IA   3877
#define IC  29573

double
gen_random(double max) {
static long last = 42;
return( max * (last = (last * IA + IC) % IM) / IM );
}

void
heapsort(int n, double *ra) {
int i, j;
int ir = n;
int l = (n >> 1) + 1;
double rra;

for (;;) {
if (l > 1) {
rra = ra[--l];
} else {
rra = ra[ir];
ra[ir] = ra[1];
if (--ir == 1) {
ra[1] = rra;
return;
}
}
i = l;
j = l << 1;
while (j <= ir) {
if (j < ir && ra[j] < ra[j+1]) { ++j; }
if (rra < ra[j]) {
ra[i] = ra[j];
j += (i = j);
} else {
j = ir + 1;
}
}
ra[i] = rra;
}
}

int
main(int argc, char *argv[]) {
int N = ((argc == 2) ? atoi(argv[1]) : 1);
double *ary;
int i;

ary = (double *)malloc((N+1) * sizeof(double));
for (i=1; i<=N; i++) {
ary[i] = gen_random(1);
}

heapsort(N, ary);

cout.precision(10);
cout << ary[N] << endl;

free(ary);
return(0);
}

```