组合算法

转自：http://www.cocoachina.com/bbs/read.php?tid=113856

- (NSMutableArray *)zuHeSuanFa:(NSMutableArray *)array chooseCount:(int)m
{     
    int n = [array count];

    if (m > n)
    {
        return nil;
    }

    NSLog(@"从1到%d中取%d个数的组合。。。",n,m);

    NSMutableArray *allChooseArray = [[NSMutableArray alloc] init];
    NSMutableArray *retArray = [array copy];

    // (1,1,1,0,0)
    for(int i=0;i < n;i++)
    {
        if (i < m)
        {
            [array replaceObjectAtIndex:i withObject:@"1"];
        }
        else 
        {
            [array replaceObjectAtIndex:i withObject:@"0"];
        }
    }

    NSMutableArray *firstArray = [[NSMutableArray alloc] init];

    for(int i=0; i<n; i++)
    {
        if ([[array objectAtIndex:i] intValue] == 1) 
        {
// [firstArray addObject:[NSString stringWithFormat:@"%d",i+1]];
            [firstArray addObject:[retArray objectAtIndex:i]];
        }
    }

    [allChooseArray addObject:firstArray];
// [firstArray release];

    int count = 0;
    for(int i = 0; i < n-1; i++)
    {
        if ([[array objectAtIndex:i] intValue] == 1 && [[array objectAtIndex:(i + 1)] intValue] == 0)
        {
            [array replaceObjectAtIndex:i withObject:@"0"];
            [array replaceObjectAtIndex:(i + 1) withObject:@"1"];

            for (int k = 0; k < i; k++)
            {
                if ([[array objectAtIndex:k] intValue] == 1)
                {
                    count ++;
                }
            }
            if (count > 0)
            {
                for (int k = 0; k < i; k++)
                {
                    if (k < count)
                    {
                        [array replaceObjectAtIndex:k withObject:@"1"];
                    }
                    else 
                    {
                        [array replaceObjectAtIndex:k withObject:@"0"];
                    }
                }
            }

            NSMutableArray *middleArray = [[NSMutableArray alloc] init];

            for (int k = 0; k < n; k++)
            {
                if ([[array objectAtIndex:k] intValue] == 1)
                {
// [middleArray addObject:[NSString stringWithFormat:@"%d",k + 1]];
                    [middleArray addObject:[retArray objectAtIndex:k]];
                }
            }

            [allChooseArray addObject:middleArray];
// [middleArray release];

            i = -1;
            count = 0;
        }
    }

    return allChooseArray;
}