栈的类模板及其应用

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1.栈的类模板：

#ifndef STACK_H#define STACK_H#include <cassert> template <class T, int SIZE = 50>class Stack {private:T list[SIZE];int top;public:Stack();void push(const T &item);T pop();void clear();const T &peek() const;bool isEmpty() const;bool isFull() const;};//模板的实现template <class T, int SIZE>Stack<T, SIZE>::Stack() : top(-1) { }template <class T, int SIZE>void Stack<T, SIZE>::push(const T &item) {assert(!isFull());list[++top] = item;}template <class T, int SIZE>T Stack<T, SIZE>::pop() {assert(!isEmpty());return list[top--];}template <class T, int SIZE>const T &Stack<T, SIZE>::peek() const {assert(!isEmpty());return list[top];   //返回栈顶元素}template <class T, int SIZE>bool Stack<T, SIZE>::isEmpty() const {return top == -1;}template <class T, int SIZE>bool Stack<T, SIZE>::isFull() const {return top == SIZE - 1;}template <class T, int SIZE>void Stack<T, SIZE>::clear() {top = -1;}#endif  //STACK_H

2.用栈模板实现一个计算器：

实现一个简单的整数计算器，能够进行加、减、乘、除和乘方运算。使用时算式采用后缀输入法，每个操作数、操作符之间都以空白符分隔。例如，若要计算"3+5"则输入"3 5 +"。乘方运算符用"^"表示。每次运算在前次结果基础上进行，若要将前次运算结果清除，可键入"c"。当键入"q"时程序结束。

计算器类定义如下：

//Calculator.h#ifndef CALCULATOR_H#define CALCULATOR_H#include <iostream>#include <sstream>#include <cmath>#include "Stack.h"  // 包含栈类模板定义文件using namespace std;class Calculator {  //计算器类private:Stack<double> s;    // 操作数栈void enter(double num); //将操作数num压入栈//连续将两个操作数弹出栈，放在opnd1和opnd2中bool getTwoOperands(double &opnd1, double &opnd2);void compute(char op);  //执行由操作符op指定的运算public:void run();     //运行计算器程序void clear();   //清空操作数栈};//工具函数，用于将字符串转换为实数inline double stringToDouble(const string &str) {istringstream stream(str);  //字符串输入流double result;stream >> result;return result;}void Calculator::enter(double num) {    //将操作数num压入栈s.push(num);}bool Calculator::getTwoOperands(double &opnd1, double &opnd2) {if (s.isEmpty()) {  //检查栈是否空cerr << "Missing operand!" << endl;return false;}opnd1 = s.pop();    //将右操作数弹出栈if (s.isEmpty()) {  //检查栈是否空cerr << "Missing operand!" << endl;return false;}opnd2 = s.pop();    //将左操作数弹出栈return true;}void Calculator::compute(char op) { //执行运算double operand1, operand2;bool result = getTwoOperands(operand1, operand2);if (result) {   //如果成功，执行运算并将运算结果压入栈switch (op) {case '+': s.push(operand2 + operand1); break;case '-': s.push(operand2 - operand1); break;case '*': s.push(operand2 * operand1); break;case '/': if (operand1 == 0) {    //检查除数是否为0  cerr << "Divided by 0!" << endl;  s.clear();    //除数为0时清空栈}  else  s.push(operand2 / operand1);break;case '^': s.push(pow(operand2, operand1)); break;default:  cerr << "Unrecognized operator!" << endl;break;}cout << "= " << s.peek() << " ";    //输出本次运算结果 }elses.clear();  //操作数不够，清空栈}void Calculator::run() { //读入并处理后缀表达式string str;while (cin >> str, str != "q") {switch (str[0]) {case 'c': s.clear(); break;case '-': //遇'-'需判断是减号还是负号if (str.size() > 1)enter(stringToDouble(str));elsecompute(str[0]);break;case '+':   //遇到其它操作符时case '*':case '/':case '^':compute(str[0]);   break;default: //若读入的是操作数，转换为整型后压入栈enter(stringToDouble(str)); break;}}}void Calculator::clear() {  //清空操作数栈s.clear();}#endif //CALCULATOR_H

3.测试函数：

#include <iostream>#include "Calculator.h"using namespace std;int main() {Calculator c;c.run();return 0;}

测试结果：

来自清华大学MOOC课件

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