无序排列组合的计算

1. n个数中取出m个的组合数（ 例如：从1，2，3，4随机取出2个数，一共有6种）

-(int)getCountBets:(int)n selectCount:(int) m{
    
    int minRange = m;
    
    
    long num1 = 1;
    
    for (int i = 1; i<=minRange; i++) {
        
        num1 = num1 * i;
        
    }
    
    long num2 = 1;
    for (int i = (int)n; I>n - minRange; i--) {
        num2 = num2 * i;
        
    }
    
    int NewtotalZhus = (int)(num2/num1);
    
    return NewtotalZhus;
}

2.表示从n个元素中取出m个元素的取法数(把所有的可能性列举出来)

- (void)combine:(int)n index:(int)k temp:(NSString *)str
{
    
    for(int i = n; i >= k; i--)
    {
        if(k > 1)
        {
            
//            [self combine:i-1 index:k-1 temp:[NSString stringWithFormat:@"%@%@",str,[dataArr objectAtIndex:i-1]]];
            
             [self combine:i-1 index:k-1 temp:[NSString stringWithFormat:@"%@,%d",str,i-1]];
            
        } else
        {
            
//         NSLog(@"%@",[NSString stringWithFormat:@"排列可能性%@%@",str,[dataArr objectAtIndex:i-1]]);
            
            NSString*oddsIndxStr;
            
             oddsIndxStr = [NSString stringWithFormat:@"%@,%d",str,i-1];
           
            
            [_oddsIndxArray addObject:oddsIndxStr];
            
            NSLog(@"%@",oddsIndxStr);
            
        }
    }
    
}

调用

  [self combine:(int)dataArr.count index:inx temp:@""];