两种快速打乱NSMutableArray的方法

1。利用交换

// NSMutableArray_Shuffling.h

#if TARGET_OS_IPHONE
#import <UIKit/UIKit.h>
#else
#include <Cocoa/Cocoa.h>
#endif

// This category enhances NSMutableArray by providing
// methods to randomly shuffle the elements.
@interface NSMutableArray (Shuffling)
- (void)shuffle;
@end


// NSMutableArray_Shuffling.m

#import "NSMutableArray_Shuffling.h"

@implementation NSMutableArray (Shuffling)

- (void)shuffle
{
NSUInteger count = [self count];
for (NSUInteger i = 0; i < count; ++i) {
// Select a random element between i and end of array to swap with.
int nElements = count - i;
int n = (random() % nElements) + i;
[self exchangeObjectAtIndex:i withObjectAtIndex:n];
}
}

@end

2。利用排序

int randomSort(id obj1, id obj2, void *context ) {
// returns random number -1 0 1
return (random()%3 - 1); 
}

- (void)shuffle {
// call custom sort function
[puzzles sortUsingFunction:randomSort context:nil];

// show in log how is our array sorted
int i = 0;
for (Puzzle * puzzle in puzzles) {
NSLog(@" #%d has index %d", i, puzzle.index);
 i++;
}
}
log output:
#0 has index #6
#1 has index #3
#2 has index #9
#3 has index #15
#4 has index #8
#5 has index #0
#6 has index #1
#7 has index #4
#8 has index #7
#9 has index #12
#10 has index #14
#11 has index #16
#12 has index #17
#13 has index #10
#14 has index #11
#15 has index #13
#16 has index #5
#17 has index #2

you may as well compare obj1 with obj2 and decide what you want to return possible values are:

    
 
     
NSOrderedAscending = -1
 
     
NSOrderedSame = 0
 
     
NSOrderedDescending = 1