如何找到任何整数值的排列和组合？

Question

我想要得到Objective C中的排列和组合。我已经发现了这两种情况，但我的代码中有一些问题，我不知道它发生在哪里。实际上，我想打印文本字段中的值，但它打印的是我输入的最后一个值。我使用的代码如下所示。请帮帮我..

    typedef enum{Power,Exponent,nCr,nPr} CalcOperation;
    NSString *storage;
    CalcOperation operation;
   -(IBAction)combination{ 
    operation = nPr; 
    storage = label.text;
    textField.text=@"";
    label.text = @"";
    }

   -(int) factorial:(int)n{
   int d = n;
   int temp = 1;
   for(int b = 2; b <= d; b++){
    temp = temp*b;
   }
  //NSLog(@"the factorials is = %i",temp);

  return temp;
 }

 -(IBAction)equalButton{
  float tempo = [storage floatValue];
  float b = [label.text floatValue];
  NSString *val = [[NSString alloc]initWithFormat:@"%f" , b];  

    switch(operation) {
     case nCr:

     textField.text = [[NSString alloc]initWithFormat:@"%f",[self factorial:tempo] / ([self factorial:[val floatValue]] * [self factorial:tempo-[val floatValue]])]; 
            //textField.text = [[NSString alloc]initWithFormat:@"%f",[val floatValue]+tempo+10];
          NSLog(@"combination %d",[self factorial:tempo] / ([self factorial:[val floatValue]] * [self factorial:tempo-[val floatValue]]));
            break;
    case nPr:

            textField.text = [[NSString alloc]initWithFormat:@"%f",[self factorial:tempo] / [self factorial:tempo-[val floatValue]]]; 
           NSLog(@"permutations %d",[self factorial:tempo] / ([self factorial:tempo-[val floatValue]]));
            break;  `
                  }
                }

Answer 1

//计算nCr，其中n=节拍，r=b

int tempo = [storage intValue];
int b = [label.text intValue];

float tempCb =  (float)[self factorial:tempo] / ([self factorial:b] * [self factorial:tempo-b])]; 

            break;