C++实现一个简单的计算器2.0 增强稳定版

Posted 2021-06-09 Jing Sir

如下所示，这是一个简单的计算器2.0  增强稳定版：

输入算式，输出结算结果。

#include<iostream>
#include<cmath>
#include<sstream>
#include<cstdio>
using namespace std;
template <class T>
class Stack
{
	private :
		T data[1000];
		int Top;
		int f;
	public :
		Stack()
		{
			Top=0;
			f=1;
		}
		void clear()
		{
			Top=0;
		}
		bool is_correct()
		{
			if(f) return true;
			return false;
		}
		T pop()
		{
			if (Top<=0)
            {
				f=0;
				return data[0];
			}
			Top--;
			return data[Top];
		}
		void push(T x)
		{
			if(Top>=1000)
            {
				cout<<"栈满溢出，错误！"<<endl;
				return;
			}
			data[Top++]=x;
		}
		T top()
		{
			if(Top<=0)
            {
				f=0;
				return data[0];
			}
			return data[Top-1];
		}
		bool is_empty()
		{
			if(Top<=0) return true;
			return false;
		}
};

class Calculator
{
	private :
		string postfixExp;
		string infixExp;
		double ans;
		int f ;
	public :
		Calculator(string s="")
		{
			infixExp=s;
			ans=0;
			f=1;
		}
		void display()
		{
			if(1)
            {
				cout<<"表达式错误"<<endl;
				return ;
			}
			cout<<"后缀表达式为："<<postfixExp<<endl;
			cout<<"表达式的值为：";
			printf("%.2f\\n",ans);
		}
		double calculate(string infixExp)
		{
			this->infixExp= infixExp;
			if (infix_to_postfix())
            {
				return ans=cal_postfix();
			}
			else
			{
				f=0;
				cout<<"语法错误，请检查表达式"<<endl;
				return 0.0;
			}
		}

		bool infix_to_postfix()
		{
            f = 1;
            Stack<char> stk;
            int a_num_end=0,is_negative=0;
            string result="#";
            stk.push('#');
            for (int i=0; i<infixExp.length(); i++)
            {
                char c = infixExp[i];
                if(c=='-'&&(i==0||infixExp[i-1]=='('))
                {
                    result+='-';
                    is_negative=1;
                    continue;
                }
                if((c<='9'&&c>='0')||c=='.')
                {
                    if(a_num_end&&!is_negative)
                    {
                        result+='#';
                    }
                    is_negative=0;
                    result+=c;
                    a_num_end=0;
                }
                else
                {
                    a_num_end=1;
                    if(c=='(') stk.push('(');
                    else if (c==')')
                    {
                        while (stk.top()!='(')
                        {
                            if (!stk.is_correct())
                            {
                                f = 0;
                                return false;
                            }
                            result+='#';
                            result+=stk.pop();
                        }
                        stk.pop();
                        if (!stk.is_correct())
                        {
                            f = 0;
                            return false;
                        }
                    }
                    else
                    {
                        int p = get_priority(c);
                        if (p==-1) return false;
                        while (p<=get_priority(stk.top()))
                        {
                            if (!stk.is_correct())
                            {
                                f = 0;
                                return false;
                            }
                            result+='#';
                            result+=stk.pop();
                        }
                        stk.push(c);
                    }
                }
            }
            while (stk.top()!='#')
            {
                if (!stk.is_correct())
                {
                    f = 0;
                    return false;
                }
                result+='#';
                result+=stk.pop();
            }
            result+='#';
            postfixExp = result;
            return true;
        }

		double  cal_postfix()
		{
            int l = postfixExp.length();
            Stack<double> stk1;
            for (int i=1; i<l; i++)
            {
                char c = postfixExp[i];
                if (c=='#') continue;
                if((c=='-'&&postfixExp[i+1]!='#')||(c>='0'&&c<='9'))
                    stk1.push(read_num(postfixExp,&i));
                else
                {
                    double y  = stk1.pop();
                    if (!stk1.is_correct())
                    {
                        f = 0;
                        return false;
                    }
                    double x = stk1.pop();
                    if (!stk1.is_correct())
                    {
                        f = 0;
                        return false;
                    }
                    stk1.push(cal(x,y,c));
                }
            }
            return stk1.pop();
        }

		double cal(double num1 ,double num2,char op)
		{
			switch(op)
			{
				case '+':
					return num1+num2;
				case '-':
					return num1-num2;
				case '*':
					return num1*num2;
				case '/':
					if (num2==0)
                    {
						f = 0;
						cout<<"除数不能为零"<<endl;
						return 0;
					}
					return num1/num2;
				default:
					return 0.0;
			}
		}

		string change(double x)
		{
			int y = (int)(x*10000),yy = y%10000;
			stringstream ss;
			ss<<y/10000<<'.'<<yy/1000<<(yy%1000)/100<<(yy%100)/10<<(yy%10);
			string r;
			ss>>r;
			int i;
			for (i=r.length()-1; i>=0; i--)
				if(r[i]!='0') break;
			if (r[i]=='.') i--;
			return  r.assign(r,0,i+1);
		}


		int get_priority(char c)
		{
			switch(c)
			{
				case '+':
				case '-':
					return 1;
				case '*':
				case '/':
					return 2;
				case '(':
					return 0;
				case ')':
					return 0;
				case '#':
					return -2;
				default:
					return -1;
			}
		}

		double read_num(string s,int *pos)
		{
			double x=0;
			int flag=0,w=0,h=1,i;
			if(s[(*pos)]=='-')
            {
				(*pos)++;
				h=-1;
			}
			for ( i=(*pos); i<s.length(); i++)
				if (s[i]!='#')
					if(s[i]=='.')
					{
						flag=1;
					}
                    else
                    {
						if(flag) w++;
						x=x*10+s[i]-'0';
					}
				else  break;
			(*pos)=i;
			return x/pow(10,w)*h;
		}
};

int main()
{
	Calculator c;
	string formula;
	while (1)
    {
		cout<<"输入要计算的表达式："<<endl;
		cin>>formula;
		if(formula.length()==1&&formula[0]=='Q') break;
		c.calculate(formula);
		c.display();
	}
	return 0;
}