#import <Foundation/Foundation.h>

typedef NSArray *(^SOfN)(id);

SOfN s_of_n_creator(int n) {
  NSMutableArray *sample = [NSMutableArray arrayWithCapacity:n];
  __block int i = 0;
  return [[^(id item) {
    i++;
    if (i <= n) {
      [sample addObject:item];
    } else if (rand() % i < n) {
      [sample replaceObjectAtIndex:rand() % n withObject:item];
    }
    return sample;
  } copy] autorelease];
}

int main(int argc, const char *argv[]) {
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

  NSCountedSet *bin = [[NSCountedSet alloc] init];
  for (int trial = 0; trial < 100000; trial++) {
    SOfN s_of_n = s_of_n_creator(3);
    NSArray *sample;
    for (int i = 0; i < 10; i++)
      sample = s_of_n([NSNumber numberWithInt:i]);
    [bin addObjectsFromArray:sample];
  }
  NSLog(@"%@", bin);
  [bin release];

  [pool release];
  return 0;
}