中缀表达式求值

#ifndef __CALCULATIONFORMULA_HEAD__
#define __CALCULATIONFORMULA_HEAD__
#include <iostream>
#include <stack>
#include <cstdio>
#include <string>
#include <cstdio>

using namespace std;

class CalculatiomFormula
{
public:
    CalculatiomFormula(string _formula)
    {
        s1 = _formula+"=";
        s2 = "";
    }
    //得到结果
    static double getValueByStr(string _formula)
    {
        CalculatiomFormula* pCalculatiomFormula = new CalculatiomFormula(_formula);
        pCalculatiomFormula->deal();
        double reslut = pCalculatiomFormula->countt();
        return reslut;
    }
private:
    string s1,s2;
    stack<char> s;
    stack<double> c;
public:
    void init()
    {
        while(!s.empty())
            s.pop();
        while(!c.empty())
            c.pop();
    }

    int pro(char ch)
    {
        switch(ch)
        {
            case ‘+‘:
            case ‘-‘:return 1;
            case ‘*‘:
            case ‘/‘:return 2;
            default :return 0;
        }
    }

    void deal()
    {
        init();
        int i=0,len=s1.length();
        s.push(‘#‘);
        while(i<len-1)
        {
            if(s1[i]==‘(‘)
                s.push(s1[i++]);
            else if(s1[i]==‘)‘)
            {
                while(s.top()!=‘(‘)
                {
                    s2+=s.top();
                    s2+=‘ ‘;
                    s.pop();
                }
                s.pop();
                i++;
            }
            else if(s1[i]==‘+‘||s1[i]==‘-‘||s1[i]==‘*‘||s1[i]==‘/‘)
            {
                while(pro(s.top())>=pro(s1[i]))
                {
                    s2+=s.top();
                    s2+=‘ ‘;
                    s.pop();
                }
                s.push(s1[i]);
                i++;
            }
            else
            {
                while(s1[i]<=‘9‘ && s1[i]>=‘0‘||s1[i]==‘.‘)
                    s2+=s1[i++];
                s2+=‘ ‘;
            }
        }
        while(s.top()!=‘#‘)
        {
            s2+=s.top();
            s.pop();
            s2+=‘ ‘;
        }
    }

    double countt()
    {
        
        int len=s2.length(),i=0;
        double y,x;
        while(i<len)
        {
            if(s2[i]==‘ ‘)
                i++;
            else
            {
                switch(s2[i])
                {
                    case ‘+‘:x=c.top();c.pop();x+=c.top();c.pop();i++;break;
                    case ‘-‘:x=c.top();c.pop();x=c.top()-x;c.pop();i++;break;
                    case ‘*‘:x=c.top();c.pop();x*=c.top();c.pop();i++;break;
                    case ‘/‘:x=c.top();c.pop();x=c.top()/x;c.pop();i++;break;
                    default :
                    {
                        x=0.0;
                        while(s2[i]<=‘9‘&&s2[i]>=‘0‘)
                            x=x*10+(s2[i++]-‘0‘);
                        if(s2[i]==‘.‘)
                        {
                            i++;
                            double k=10.0;y=0.0;
                            while(s2[i]<=‘9‘&&s2[i]>=‘0‘)
                            {
                                y+=(s2[i++]-‘0‘)/k;
                                k*=10;
                            }
                            x+=y;
                        }
                    }
                }
                c.push(x);
            }
        }
        return c.top();
    }
};
#endif // __CALCULATIONFORMULA_HEAD__