求大神告知这串代码如何修改，谢谢啦（C语言初学者

#include<stdio.h>
#include<string.h>
int calculate(int a,int b,char op)
{
    switch (op)
    {
        case'a':
        return a+b;
        case'b':
        return a-b;
        case'c':
        return a*b;
        default:
        return 0;
    }
}
int main()
{
  int n;
  scanf("%d",&n);
  char op;
  int num1,num2;
  for(int i=0;i<n;i++)
  {
      
      scanf("%c %d %d",&op,&num1,&num2);
      int result=calculate(num1,num2,op);
      char equation[100];
      sprintf(equation,"%d%c%d=%d",num1,op,num2,result);
      printf("%s\n",result);
      printf("%d\n",(int)strlen(equation));
  }
  return 0;
    
    
}