中缀表达式计算C++实现

#include "Calculator.h" Calculator::Calculator(){ } void Calculator::processInput(){ char c; while((c=getchar()) != '#'){ charQueue.push(c); } /* while(!charQueue.empty()){ cout<<charQueue.front()<<" "; charQueue.pop(); } cout<<endl; */ } bool Calculator::isPriority(char optr1,char optr2){//optr1 is the icp,and the optr2 is the isp if(optr1 == '^'){ if(optr2 == '^') return false; else return true; } else if(optr1 == '*' || optr1 == '/' || optr1 == '%'){ if(optr2 == '^' || optr2 == '*' || optr2 == '%' ||optr2 == '*') return false; else return true; } else if(optr1 == '+' || optr1 == '-'){ return false; } return false; } int Calculator::getResult(int num1,int num2,char optr){ int result = 0; switch(optr){ case '^': result = 1; for(int i=0;i<num1;i++) result *= num2; break; case '*': result = num1*num2; break; case '/': result = num2/num1; break; case '%': result = num2%num1; break; case '+': result = num1+num2; break; case '-': result = num2-num1; break; default: break; } return result; } void Calculator::process(){ char c; while(!charQueue.empty()){ c = charQueue.front();//get the front element charQueue.pop(); if(isdigit(c)){//the char c is a digit int temNum = c-'0'; while(!charQueue.empty() && isdigit(charQueue.front())){ c = charQueue.front(); charQueue.pop(); temNum = (temNum*10) + (c-'0');//calculate the current result } //push the num to the numStack numStack.push(temNum); }else{//it must be a optr if(c != '^' && c != '%' && c != '/' && c != '*' && c != '+' && c != '-'){ cout<<"invalide input!please check!"<<endl; return; } else{ if(optrStack.empty()){//the optrStack is empty optrStack.push(c); } else{//the optrStack is unempty if(isPriority(c,optrStack.top())){//icp>isp,push the icp optrStack.push(c); }else{//icp<=isp,pop one from optrStack,pop two from numStack,getResult,push the //result to the numStack,push the icp to optrStack char temOptr = optrStack.top(); optrStack.pop(); int temNum1 = numStack.top(); numStack.pop(); int temNum2 = numStack.top(); numStack.pop(); //get the result int temResult = getResult(temNum1,temNum2,temOptr); //push the result numStack.push(temResult); //push the c optrStack.push(c); } } } } } //finish the input,then get the final result while(!optrStack.empty()){//while the optrStack is unEmpty char temOptr = optrStack.top(); optrStack.pop(); int temNum1 = numStack.top(); numStack.pop(); int temNum2 = numStack.top(); numStack.pop(); //get the result int temResult = getResult(temNum1,temNum2,temOptr); numStack.push(temResult); } int finalResult = 0; if(!numStack.empty()){ finalResult = numStack.top(); numStack.pop(); } //check the numStack if(!numStack.empty()){ cout<<"There is an error in the expression,please check!"; return; }else{ cout<<"The final result of the input expression is: "<<finalResult<<endl; return; } } void Calculator::clean(){ while(!optrStack.empty()){ optrStack.pop(); } while(!numStack.empty()) numStack.pop(); while(!charQueue.empty()) charQueue.pop(); } void Calculator::calculate(){ processInput(); process(); clean(); }