排列组合计算公式

#pragma mark - 组合计算公式
- (NSMutableArray *)zuHeSuanFa:(NSMutableArray *)array chooseCount:(int)m
{
    int n = [array count];
    if (m > n)
    {
        return nil;
    }
    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"];
            
            // i = 2, (1,1,0,1,0)
            
            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)
                    {
                        // k = 1, (1,1,0,1,0)
                        [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;
}