习题6-7 简单计算器 (20分)

习题6-7 简单计算器 (20分)

代码：

#include <stdio.h>
int main()
{
 char regular[1024];
 scanf("%s", &regular);
 int i = 0, sum = 0, num = 0;
 char reg;
 while (regular[i] >= '0' && regular[i] <= '9') {
  sum = sum * 10 + (regular[i] - '0');
  i++;
 }
 while (1){
  if (regular[i] == '=') break;
  if (regular[i] == '+' || regular[i] == '-' || regular[i] == '*' || regular[i] == '/') {
   reg = regular[i];
   i++;
  }
  else if (regular[i] >= '0' && regular[i] <= '9'){
   num = 0;
      while (regular[i] >= '0' && regular[i] <= '9') {
       num = num *10 + (regular[i] - '0');
       i++;
      }
      if (num == 0 && reg == '/') {
       printf("ERROR");
       return 0;
   } 
   switch (reg) {
       case '+': sum += num; break;
       case '-': sum -= num; break;
       case '*': sum *= num; break;
       case '/': sum /= num; break;
      }
  }
  else {
   printf("ERROR");
   return 0;
  }
 }
 printf("%d", sum);
 return 0;
}