这次计算题程序已收官完成，再次进行分析和总结。
一、设计思路
1. 从txt读取算式。
2. 将算式由中缀转后缀。
3. 计算后缀算式并与用户输入答案进行比较，答案正确提示正确，答案错误提示错误并输出正确的答案。与此同时，统计用户正确与错误的次数以及题目的总数量。
4. 重复，直到算式全部计算完成，输出统计的正确错误数和题目的总数量。
二、具体实现
本程序运用了面向对象的设计思路。经过资料搜索，我发现有很多参考的程序。它们已经实现了中缀转后缀并输出正确结果并统计正误的功能，但无法计算分数。因此，我在此基础上进行了改进，增加了一个Fraction类。其把所有的整数都转换成了分数形式，并且重载了所有的运算符。之后，在重用的程序中把所有的定义的变量都定义为Fraction类型的就可以了。
以下是新增的Fraction类。
#pragma once
#include <iostream>
using namespace std;
class Fraction
{
public:
Fraction();
Fraction(int n);
Fraction(int n, int d);
~Fraction();
int numerator;
int denominator;
Fraction operator + (Fraction f);
Fraction operator - (Fraction f);
Fraction operator * (Fraction f);
Fraction operator / (Fraction f);
bool operator == (Fraction f);
friend istream &operator >> (istream &in, Fraction &f);
friend ostream &operator << (ostream &out, Fraction &f);
void reduction();
int get_gcd(int a, int b);
};
#include "stdafx.h"
#include "Fraction.h"
Fraction::Fraction()
{
}
Fraction::Fraction(int n) :numerator(n), denominator(1)
{
}
Fraction::Fraction(int n, int d) : numerator(n), denominator(d)
{
}
Fraction::~Fraction()
{
}
Fraction Fraction::operator + (Fraction f) {
return Fraction(numerator * f.denominator + denominator * f.numerator, denominator * f.denominator);
}
Fraction Fraction::operator - (Fraction f) {
return Fraction(numerator * f.denominator - denominator * f.numerator, denominator * f.denominator);
}
Fraction Fraction::operator * (Fraction f) {
return Fraction(numerator * f.numerator, denominator * f.denominator);
}
Fraction Fraction::operator / (Fraction f) {
return Fraction(numerator * f.denominator, denominator * f.numerator);
}
bool Fraction::operator == (Fraction f) {
return numerator == f.numerator && denominator == f.denominator;
}
istream& operator >> (istream &in, Fraction &f) {
in >> f.numerator;
f.denominator = 1;
char c;
in.get(c);
if (c != ‘\n‘)
{
in >> f.denominator;
}
return in;
}
ostream& operator << (ostream &out, Fraction &f) {
f.reduction();
if (f.denominator == 1)
out << f.numerator;
else
out << f.numerator << "/" << f.denominator;
return out;
}
void Fraction::reduction() {
int gcd = get_gcd(numerator, denominator);
numerator = numerator / gcd;
denominator = denominator / gcd;
if (denominator < 0)
{
numerator = -numerator;
denominator = -denominator;
}
}
int Fraction::get_gcd(int a, int b)
{
if (b == 0)
return a;
return get_gcd(b, a%b);
}
以下是网上参考的只能进行整数运算的程序的改进。
#pragma once
#include "Fraction.h"
class Expression
{
public:
Fraction Operand;
char Operator = NULL;
};
#include "stdafx.h"
#include "Expression.h"
/////////////////////////////////////////////////////////////////////////
#pragma once
#include "Expression.h"
#include <stack>
#include <fstream>
class Calculator
{
private:
stack<char> is;
stack<Fraction> ps;
Expression InfixExp[100];
Expression PostfixExp[100];
int il;
int pl;
bool GetInfixExp();
bool Transform();
bool GetTwoOperands(Fraction &opd1, Fraction &opd2);
bool Compute(char op);
ifstream ifs, ifs_line;
public:
Calculator();
~Calculator();
void Run();
};
#include "stdafx.h"
#include "Calculator.h"
Calculator::Calculator()
{
Run();
}
Calculator::~Calculator()
{
}
bool Calculator::GetInfixExp() {
char c;
int newOperand;
bool lastExpIsNum = false;
bool nextNumAddMinus = false;
char printExp[128];
ifs_line.getline(printExp, 128);
cout << printExp << " ";
while (ifs >> c, c != ‘=‘) {
switch (c) {
case ‘-‘:
if (lastExpIsNum)
{
InfixExp[il].Operator = c;
}
else
{
nextNumAddMinus = true;
il--;
}
lastExpIsNum = false;
break;
case ‘+‘:
case ‘*‘:
case ‘/‘:
case ‘(‘:
InfixExp[il].Operator = c;
lastExpIsNum = false;
break;
case ‘)‘:
InfixExp[il].Operator = c;
lastExpIsNum = true;
break;
default:
if (c >= ‘0‘ && c <= ‘9‘) {
ifs.putback(c);
ifs >> newOperand;
newOperand = nextNumAddMinus ? -newOperand : newOperand;
nextNumAddMinus = false;
InfixExp[il].Operand = Fraction(newOperand);
}
else {
return false;
}
lastExpIsNum = true;
break;
}
il++;
}
return true;
}
bool Calculator::Transform() {
bool flag;
for (int i = 0; i < il; i++) {
if (InfixExp[i].Operator == NULL) {
PostfixExp[pl].Operand = InfixExp[i].Operand;
pl++;
}
else if (InfixExp[i].Operator == ‘(‘) {
is.push(‘(‘);
}
else if (InfixExp[i].Operator == ‘)‘) {
if (is.empty()) {
return false;
}
else {
flag = false;
while (!is.empty()) {
if (is.top() != ‘(‘) {
PostfixExp[pl].Operator = is.top();
is.pop();
pl++;
}
else {
flag = true;
is.pop();
break;
}
}
if (is.empty() && !flag) {
return false;
}
}
}
else {
while (
!is.empty() &&
is.top() != ‘(‘ &&
!((is.top() == ‘+‘ || is.top() == ‘-‘) && (InfixExp[i].Operator == ‘*‘ || InfixExp[i].Operator == ‘/‘))
) {
PostfixExp[pl].Operator = is.top();
is.pop();
pl++;
}
is.push(InfixExp[i].Operator);
}
}
while (!is.empty()) {
if (is.top() == ‘(‘) {
return false;
}
else {
PostfixExp[pl].Operator = is.top();
is.pop();
pl++;
}
}
return true;
}
bool Calculator::GetTwoOperands(Fraction& opd1, Fraction& opd2) {
if (ps.empty())
return false;
opd1 = ps.top();
ps.pop();
if (ps.empty())
return false;
opd2 = ps.top();
ps.pop();
return true;
}
bool Calculator::Compute(char op) {
bool result;
Fraction operand1, operand2;
result = GetTwoOperands(operand1, operand2);
if (result) {
switch (op)
{
case ‘+‘:
ps.push(operand2 + operand1);
break;
case ‘-‘:
ps.push(operand2 - operand1);
break;
case ‘*‘:
ps.push(operand2 * operand1);
break;
case ‘/‘:
if (operand1.numerator == 0) {
cout << "除数存在0，错误！" << endl;
return false;
}
else {
ps.push(operand2 / operand1);
}
break;
}
}
return true;
}
void Calculator::Run() {
ifs = ifstream("Expressions.txt");
ifs_line = ifstream("Expressions.txt");
Fraction correct_answer, user_answer;
int correct_num = 0, wrong_num = 0;
// 输入中缀表达式
cout << "请计算下列算式：" << endl;
while (!ifs_line.eof())
{
il = 0;
pl = 0;
while (!is.empty())
is.pop();
while (!ps.empty())
ps.pop();
for (int i = 0; i < 100; i++)
{
InfixExp[i] = PostfixExp[i] = Expression();
}
if (GetInfixExp() && Transform()) {
for (int i = 0; i < pl; i++) {
if (PostfixExp[i].Operator == NULL)
ps.push(PostfixExp[i].Operand);
else {
if (!Compute(PostfixExp[i].Operator))
return;
}
}
correct_answer = ps.top();
}
else
{
cout << "算式格式错误" << endl;
return;
}
cin >> user_answer;
user_answer.reduction(), correct_answer.reduction();
if (user_answer == correct_answer)
{
correct_num++;
cout << "正确" << endl;
}
else
{
wrong_num++;
cout << "错误，正确答案是" << correct_answer << endl;
}
}
cout << "--------------------------" << endl;
cout << "共" << correct_num + wrong_num << "题，";
cout << "正确" << correct_num << "道，错误" << wrong_num << "道" << endl;
}
三、项目总结
这次项目，对我改进程序的能力有了提升。每个程序并不是一定要从零开始。我们可以利用他人的的思路和成果，再次基础上进行改进。同时，我们也应多和他人进行交流，因为这样可以更方便地获取新鲜高端的思路，对项目的完成有所广益。
时间： 2024-12-19 07:26:51