iOS：如何生成8个唯一的随机整数？ [英] iOS: How do I generate 8 unique random integers?

问题描述

我需要生成8个随机整数，但它们必须是唯一的，也就是说不重复。

I need to generate 8 random integers, but they need to be unique, aka not repeated.

例如，我想要1到8范围内的8个数字。

For example, I want 8 numbers within the range 1 to 8.

我见过arc4random，但我不确定如何让它们与众不同？

I've seen arc4random but I'm not sure how to make them unique ?

解决方案

-(NSMutableArray *)getRandomInts:(int)amount from:(int)fromInt to:(int)toInt {

  if ((toInt - fromInt) +1 < amount) {
      return nil;    
  }

  NSMutableArray *uniqueNumbers = [[[NSMutableArray alloc] init] autorelease];
  int r;
  while ([uniqueNumbers count] < amount) {

      r = (arc4random() % toInt) + fromInt;
      if (![uniqueNumbers containsObject:[NSNumber numberWithInt:r]]) {
          [uniqueNumbers addObject:[NSNumber numberWithInt:r]];
      }
  }
  return uniqueNumbers;
}

推荐答案

-(NSMutableArray *)getEightRandom {
  NSMutableArray *uniqueNumbers = [[[NSMutableArray alloc] init] autorelease];
  int r;
  while ([uniqueNumbers count] < 8) {
    r = arc4random();
    if (![uniqueNumbers containsObject:[NSNumber numberWithInt:r]]) {
      [uniqueNumbers addObject:[NSNumber numberWithInt:r]];
    }
  }
  return uniqueNumbers;
}

如果你想限制到低于某个门槛M的数字，你可以这样做：

If you want to restrict to numbers less than some threshold M, then you can do this by:

-(NSMutableArray *)getEightRandomLessThan:(int)M {
  NSMutableArray *uniqueNumbers = [[[NSMutableArray alloc] init] autorelease];
  int r;
  while ([uniqueNumbers count] < 8) {
    r = arc4random() % M; // ADD 1 TO GET NUMBERS BETWEEN 1 AND M RATHER THAN 0 and M-1
    if (![uniqueNumbers containsObject:[NSNumber numberWithInt:r]]) {
      [uniqueNumbers addObject:[NSNumber numberWithInt:r]];
    }
  }
  return uniqueNumbers;
}

如果M = 8，或者即使M接近8（例如9或者10），这需要一段时间，你可以更聪明。

If M=8, or even if M is close to 8 (e.g. 9 or 10), then this takes a while and you can be more clever.

-(NSMutableArray *)getEightRandomLessThan:(int)M {
  NSMutableArray *listOfNumbers = [[NSMutableArray alloc] init];
  for (int i=0 ; i<M ; ++i) {
    [listOfNumbers addObject:[NSNumber numberWithInt:i]]; // ADD 1 TO GET NUMBERS BETWEEN 1 AND M RATHER THAN 0 and M-1
  }
  NSMutableArray *uniqueNumbers = [[[NSMutableArray alloc] init] autorelease];
  int r;
  while ([uniqueNumbers count] < 8) {
    r = arc4random() % [listOfNumbers count];
    if (![uniqueNumbers containsObject:[listOfNumbers objectAtIndex:r]]) {
      [uniqueNumbers addObject:[listOfNumbers objectAtIndex:r]];
    }
  }
  [listOfNumbers release];
  return uniqueNumbers;
}

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