从列表中选择不带重复的随机字符填充数组 [英] Fill an array with random characters chosen from a list without duplicates

问题描述

我想用6个不同字符中的4个来填充数组，其中数组中的每个字符都不同。放入数组的字符基于switch语句。然后我想回到数组，以确保我刚刚放置的字符不是已经在数组中，如果它是我必须放入一个不同的字符。我如何做到这一点？我不想重新填充整个数组，只是这一个点。

I am trying to fill an array with 4 of 6 different characters where each character in the array is different. The character that is placed into the array is based on a switch statement. Then I want to go back through the array to make sure the character I just placed is not already in the array and if it is I have to put in a different character. How do I do this? I don't want to refill the whole array, just this one spot.

这是我到目前为止的代码，评论包括：

This is the code I have so far, comments included:

-(void) fillarray{

for (int i=0; i<4; i++)
{
    int randomNum = arc4random() % 6; // generates a random number

          switch (randomNum) // based on the number generated, it choses what color will be placed into the slot
    {
        case 1:
            colorarray[i] ='r';
            break;

        case 2:
            colorarray[i] ='o';
            break;

        case 3:
            colorarray[i] ='y';
            break;

        case 4:
            colorarray[i] ='g';
            break;
        case 5:
            colorarray[i] = 'b';

        case 6:
            colorarray[i] = 'p';

        default:
            break;
    }

    for (int j=0; j<4; j++) // runs through the array to ensure that the recently placed color does not match previous placed colors
    {
        while (j /= i)

            if (colorarray[i]==colorarray[j]) // if the color is already in the array
                                            //try again to place another color in this location

    }

推荐答案

我会根据 Fisher-Yates shuffling算法

NSArray * array = @[ @"r", @"o", @"y", @"g", @"b", @"p" ] ;
array = [ [ array shuffledArray ] subarrayWithRange:(NSRange){ .length = 4 } ] ;

其中 -shuffledArray 被添加到NSArray

Where -shuffledArray is added to NSArray by:

@implementation NSArray ( Shuffling )

-(NSArray*)shuffledArray
{
    NSMutableArray * result = [ NSMutableArray arrayWithCapacity:self.count ] ;
    [ result addObject:self[0] ] ;
    for( NSUInteger index=1, count = self.count; index < count; ++index )
    {
        int j = arc4random_uniform( (unsigned int)index ) ;
        [ result addObject:result[j] ] ;
        [ result replaceObjectAtIndex:j withObject:self[ index ] ] ;
    }

    return result ;
}

@end

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