一個簡單的計算C語言四則運算

#include<stdio.h>
#include<string.h>
int main(void)
{
char string[100];
int index = 1;
int sum = 0;
int temval = 1;
char ope, c,inope;
    memset(string, 0, 100);
    scanf("%s",string);

    sum += (string[0] - 48);
while(string[index] != '\0')
    {
        c = string[index];
switch(c)
        {
case '+':ope = '+';index++;
break;
case '-':ope = '-';index++;
break;
case '*':ope = '*';index++;
break;
case '/':ope = '/';index++;
break;
default:temval = c - 48;index++;
while(string[index] != '+'&&string[index] != '-'&&string[index] != '\0')
            {
                inope = string[index];
if(inope == '*')
                {
                    temval *= (string[++index] - 48);
                    index++;
                }
if(inope == '/')
                {
                    temval /= (string[++index] - 48);
                    index++;
                }
            }
if(ope =='+')
            {

                sum +=temval;
            }
if(ope == '-')
            {
                sum -= temval;
            }
        }
    }
    printf("\n運算式%s的值為:%d\n",string,sum);
return 0;
}

 

計算類似1+2-3*3/3的運算式,如果輸入的格式不正確，因為沒有加入判斷運算式是否正確，會出錯的。