How to randomize an NSMutableArray? [duplicate]

问题

Possible Duplicate:
iphone - nsarray/nsmutablearray - re-arrange in random order

I have an NSMutableArray that contains 20 objects. Is there any way that I could randomize their order like when you shuffle a deck. (By order I mean their index in the array)

Like if I had an array that contained:

apple
orange
pear
banana

How could I randomize the order so that I could get something like:

orange
apple
banana
pear

回答1:

Here's some sample code: Iterates through the array, and randomly switches an object's position with another.

for (int x = 0; x < [array count]; x++) {
    int randInt = (arc4random() % ([array count] - x)) + x;
    [array exchangeObjectAtIndex:x withObjectAtIndex:randInt];
}

回答2:

@interface NSArray (Shuffling)

- (NSArray *)shuffledArray;

@end

@implementation NSArray (Shuffling)

- (NSArray *)shuffledArray {
    NSMutableArray *newArray = [[self mutableCopy] autorelease];

    [newArray shuffle];
    return newArray;
}

@end

@interface NSMutableArray (Shuffling)

- (void)shuffle;

@end

@implementation NSMutableArray (Shuffling)

- (void)shuffle {
    @synchronized(self) {
        NSUInteger count = [self count];

        if (count == 0) {
            return;
        }

        for (NSUInteger i = 0; i < count; i++) {
            NSUInteger j = arc4random() % (count - 1);

            if (j != i) {
                [self exchangeObjectAtIndex:i withObjectAtIndex:j];
            }
        }
    }
}

@end

However keep in mind that this kind of shuffling is merely pseudorandom shuffling!

来源：https://stackoverflow.com/questions/6255369/how-to-randomize-an-nsmutablearray

标签

objective-c

nsmutablearray

shuffle