OC实现将N个数随机排列

 + (NSMutableArray *)randArray : (NSMutableArray *)arrayM
 {

     NSMutableArray *resultM = [[NSMutableArray alloc] initWithCapacity:arrayM.count];
     NSInteger count = arrayM.count;
     for (NSInteger i = ; i < count; i ++)
     {
         NSInteger index = arc4random_uniform((unsigned int)arrayM.count);
         [resultM addObject:[arrayM objectAtIndex:index]];
         [arrayM removeObjectAtIndex:index];

     }
     return resultM;
 }