//学校c++第一节实验课作业，难点在于小数点后面的数据提取
#include <iostream>
#include <string>
#include <stack>
#include <math.h>
using namespace std;
int main()
{
//存放操作符
stack<char>oper_reserve;
string s;
int flag=0;
cout<<"请输入计算式:";
cin>>s;
for(int i=0; i<s.size(); i++)
{
switch(s[i])
{
case '(':
cout<<"操作符：左小括号"<<endl;
oper_reserve.push(s[i]);
break;
case '[':
cout<<"操作符：左中括号"<<endl;
oper_reserve.push(s[i]);
break;
case'{':
cout<<"操作符：左大括号"<<endl;
oper_reserve.push(s[i]);
break;
case '+':
cout<<"操作符：加号"<<endl;
break;
case '-':
cout<<"操作符：减号"<<endl;
break;
case '*':
cout<<"操作符：乘号"<<endl;
break;
case '/':
cout<<"操作符：除号"<<endl;
break;
case ')':
if(oper_reserve.empty())
cout<<"操作符：右小括号匹配错误"<<endl;
else
{
if (oper_reserve.top()=!'(')
{
cout<<"操作符：右小括号 匹配错误"<<endl;
oper_reserve.pop();
}
else
{
cout<<"操作符：右小括号"<<endl;
oper_reserve.pop();
}
}
break;
case ']':
if(oper_reserve.empty())
cout<<"操作符：右中括号 匹配错误"<<endl;
else
{
if (oper_reserve.top()=!'[')
{
cout<<"操作符：右中括号 匹配错误"<<endl;
oper_reserve.pop();
}
else
{
cout<<"操作符：右中括号"<<endl;
oper_reserve.pop();
}
}
break;
case'}':
if(oper_reserve.empty())
cout<<"操作符：右大括号 匹配错误"<<endl;
else
{
if (oper_reserve.top()=!'{')
{
cout<<"操作符：右大括号 匹配错误"<<endl;
oper_reserve.pop();
}
else
{
cout<<"操作符：右大括号"<<endl;
oper_reserve.pop();
}
}
break;
}
if((s[i]<'9'&&s[i]>'0')||s[i]=='.') //若扫描到数字
{
float cur_num=0;
float decimal=0;
int j;
j=i;
while(j<s.size()&&(s[j]<'9'&&s[j]>'0')||s[j]=='.')
{
if(s[j]=='.')
{ flag=j; //记录小数点位置
int k=j;
while(k<s.size()&&s[k+1]<'9'&&s[k+1]>'0')
{
double index=k+1-flag; //index代表小数点后x位
decimal=(s[k+1]-'0')*pow(0.1,index)+decimal; //循环求小数部分
k++;
i=k;
j=j+index+1; //赋值后s[j]指向数字后面一位符号，如12.3+ 此时s[j]是+
}
}
else
{
cur_num=cur_num*10+(s[j]-'0');
j++;
i=j-1;
}
}
float sum=cur_num+decimal;
cout<<"操作数:"<<sum<<endl;
}
}
return 0;
}