cal exp

最新推荐文章于 2021-11-24 11:10:32 发布

原创最新推荐文章于 2021-11-24 11:10:32 发布 · 896 阅读

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本文介绍了一个简单的四则运算解析器实现，通过C语言完成基本的乘除加减操作，并根据输入字符串进行运算顺序处理。文章展示了如何使用switch-case结构来实现不同的运算逻辑。

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#include <stdio.h>
#include <string.h>

int cal(int a, int b, char op)
{
   switch (op)
   {
       case '*':
           return a * b;;
           break;
       case '/':
           return (int)(a / b);
           break;
       case '+':
           return a + b;
           break;
       case '-':
           return a - b;
           break;
   }
}

int main()
{
   char str[7];
   int mark1, mark2, mark3;
   int val1, val2, val3, res;
   res = 0;
   mark1 = 0;
   mark2 = 0;
   mark3 = 0;
   gets(str);

   if (str[1] == '*' || str[1] == '/')
   {
       mark1 = 1;
       val1 = cal(str[0]-'0', str[2]-'0', str[1]);
   }
   if (str[3] == '*' || str[3] == '/')
   {
       mark2 = 1;
       if (mark1)
           val2 = cal(val1, str[4] - '0', str[3]);
       else
           val2 = cal(str[2]-'0', str[4]-'0',str[3]);
   }
   if (str[5] == '*' || str[5] == '/')
   {
       mark3 = 1;
       if (mark2)
           val3 = cal(val2, str[6]-'0', str[5]);
       else
           val3 = cal(str[4]-'0', str[6]-'0', str[5]);
   }

   if (mark3 && mark2 && mark1)
       res = val3;
   else if (mark1 && mark2)
       res = cal(val2, str[6]-'0', str[5]);
   else if (mark1 && mark3)
       res = cal(val1, val3, str[3]);
   else if (mark2 && mark3)
       res = cal(str[0]-'0',val3, str[1]);
   else if (mark1)
       res = cal(cal(val1, str[4]-'0', str[3]), str[6]-'0', str[5]);
   else if (mark2)
       res = cal(cal(str[0]-'0', val2, str[1]), str[6]-'0', str[5]);
   else if (mark3)
       res = cal(cal(str[0]-'0', str[2]-'0',str[1]), val3, str[3]);
   else
       res = cal(cal(cal(str[0]-'0',str[2]-'0',str[1]), str[4]-'0',str[3]),str[6]-'0',str[5]);

   printf("%s = %d\n", str, res);
}