if-else條件改成以函式指標陣列(array of function pointer)的方式改寫

#include "stdio.h"

#include "stdlib.h"

int plus(int a, int b) { return a + b; }
int minus(int a, int b) { return a - b; }
int multiply(int a, int b) { return a * b; }
int divided(int a, int b) { return a / b; }
int main()
{
 int a, c;
 char b;
 printf("key a Function \nEX: 1 + 1\n");
 scanf("%i %c %i", &a, &b, &c);

 if (b == '+')
  printf("%d %c %d = %d\n", a, b, c, plus(a, c));
 else if (b == '-')
  printf("%d %c %d = %d\n", a, b, c, minus(a, c));
 else if (b == '*')
  printf("%d %c %d = %d\n", a, b, c, multiply(a, c));
 else if (b == '/')
  printf("%d %c %d = %d\n", a, b, c, divided(a, c));
}

 =========================================================================

#include"stdio.h"

int plus(int a, int b){ return a+b; }
int minus(int a, int b){ return a-b; }
int multiply(int a, int b){ return a*b; }
int divided(int a, int b){ return a/b; }

int main(){
    int a, c;
    char b;
    scanf("%d %c %d", &a, &b, &c);
    
    int (*cmd[])(int a, int c) = {multiply, plus, NULL, minus, NULL, divided};

    printf("%d\n",cmd[b-42](a,c));  // '*' ASCII = 42(0x2a)  ,'+' ASCII = 43 (0x2b), '-' ASCII = 45, '/' ASCII = 47    

    return 0;
}