一个堆栈，一个表达式计算器

 堆：

//Stack.h

template <class T> class Stack { public: Stack(int stack_size = 30); ~Stack(); void Push(T value); T Pop(); T Top(); bool IsEmpty(); bool IsFull(); void ClearStack(); private: int top; T* stack; int size; }; template<class T> Stack<T>::Stack(int stack_size) { size = stack_size; Stack::stack = new T[size]; Stack::top = -1; } template<class T> Stack<T>::~Stack() { delete []stack; } template<class T> void Stack<T>::Push(T value) { stack[++top] = value; } template<class T> T Stack<T>::Pop() { return stack[top--]; } template<class T> T Stack<T>::Top() { return Stack[top]; } template<class T> bool Stack<T>::IsEmpty() { return(top==-1?true:false); } template<class T> bool Stack<T>::IsFull() { return(top==(size-1)?true:false); } template<class T> void Stack<T>::ClearStack() { top = -1; } 

 

表达式计算器：

//Calculater.h
#include <string> #include <sstream> #include <vector> #include "Stack.h" using namespace std; class Calculater { public: Calculater(); ~Calculater(); int Cal(string express); private: string ParseString(string express); vector<string> MidToBehind(string express); int Compute(int a,int b,char operater); Stack<int> stack_int; Stack<char> stack_char; }; Calculater::Calculater() { } Calculater::~Calculater() { } vector<string> Calculater::MidToBehind(string express) { stringstream strstrm(express); char temp_char; string temp_str; vector<string> result_vec; while (strstrm>>temp_char) { if (temp_char!='('&&temp_char!=')'&&temp_char!='+'&&temp_char!='-'&&temp_char!='*'&&temp_char!='/'&&temp_char!='=') { strstrm.putback(temp_char); strstrm>>temp_str; result_vec.push_back(temp_str); } else if(temp_char == '(') { stack_char.Push(temp_char); } else if(temp_char == ')') { if(stack_char.IsEmpty()) { cout<<"stack is empty when push ')'"<<endl; stack_char.ClearStack(); } else { while (temp_char = stack_char.Pop(),temp_char != '(') { result_vec.push_back(string(1,temp_char)); if (stack_char.IsEmpty()) { cout<<"stack is empty when pop,not found the '('"<<endl; stack_char.ClearStack(); } } } } else if(temp_char == '+'||temp_char == '-'||temp_char == '*'||temp_char == '/') { switch (temp_char) { char temp_char_2; case '+': while (!stack_char.IsEmpty()) { temp_char_2 = stack_char.Pop(); if (temp_char_2 == '(') { stack_char.Push(temp_char_2); break; } else result_vec.push_back(string(1,temp_char_2)); } stack_char.Push(temp_char); break; case '-': while (!stack_char.IsEmpty()) { temp_char_2 = stack_char.Pop(); if (temp_char_2 == '(') { stack_char.Push(temp_char_2); break; } else result_vec.push_back(string(1,temp_char_2)); } stack_char.Push(temp_char); break; case '*': while (!stack_char.IsEmpty()) { temp_char_2 = stack_char.Pop(); if (temp_char_2 == '('||temp_char_2 == '+'||temp_char_2 == '-') { stack_char.Push(temp_char_2); break; } else result_vec.push_back(string(1,temp_char_2)); } stack_char.Push(temp_char); break; case '/': while (!stack_char.IsEmpty()) { temp_char_2 = stack_char.Pop(); if (temp_char_2 == '('||temp_char_2 == '+'||temp_char_2 == '-') { stack_char.Push(temp_char_2); break; } else result_vec.push_back(string(1,temp_char_2)); } stack_char.Push(temp_char); break; default: break; } } else if (temp_char == '=') { while (!stack_char.IsEmpty()) { result_vec.push_back(string(1,stack_char.Pop())); } } else cout<<"wrong express"<<endl; } return result_vec; } int Calculater::Compute(int a,int b,char operater) { switch(operater) { case '+': return a + b; case '-': return a - b; case '*': return a * b; case '/': if(b == 0) { cout<<"divided by 0!wrong!"<<endl; return -1; } else return a / b; default: break; } cout<<"Not return"<<endl; return -1; } int Calculater::Cal(string express) { string new_exp = ParseString(express); string str_temp; vector<string> vec_exp = MidToBehind(new_exp); for (vector<string>::iterator it = vec_exp.begin();it != vec_exp.end();it++) { str_temp = *it; if (str_temp!="+"&&str_temp!="-"&&str_temp!="*"&&str_temp!="/") { int int_temp = 0; int time = 1; for (string::iterator itr = str_temp.begin();itr != str_temp.end();itr++) { int_temp = int_temp*10 + (*itr - '0'); } stack_int.Push(int_temp); } else { int a,b; b = stack_int.Pop(); a = stack_int.Pop(); char ch = str_temp[0]; int c = Compute(a,b,ch); stack_int.Push(c); } } return stack_int.Pop(); } string Calculater::ParseString(string express) { string new_exp; bool flag = false; for (string::iterator it = express.begin();it != express.end();it++) { if (*it>='0'&&*it<='9') { if(flag) new_exp.push_back(' '); flag = false; new_exp.push_back(*it); } else { flag = true; if(it != express.begin()) new_exp.push_back(' '); new_exp.push_back(*it); } } return new_exp; }

 

//main.cpp

#include <iostream> //#include "Stack.h" #include "Calculater.h" #include <string> using namespace std; int main() { //Test The Calculater Calculater ca; string mid; getline(cin,mid); int res = ca.Cal(mid); cout<<res<<endl; }

 

说明：

Stack为堆栈模板类，Calculater为以Stack为工具实现的表达式计算器类。

输入四则表达式（包含运算数、+ - * /、(、)），输出计算结果。

（暂未提供乘方功能）。

算法原理为将中缀表达式转化为后缀表达式，再计算。