mathquestface.cpp

C++&datastructure书籍源码,以前外教提供现在与大家共享

#include <iostream>
#include <iomanip>
using namespace std; 
#include "mathquestface.h"
#include "randgen.h"
#include "strutils.h"

MathQuestion::MathQuestion()
   : myAnswer("*** error ***"),
     myNum1(0),
     myNum2(0)
{
    // nothing to initialize
}

void MathQuestion::Create()
{
    RandGen gen;  
    // generate random numbers until there is no carry
    do
    {
        myNum1 = gen.RandInt(10,49);
        myNum2 = gen.RandInt(10,49);
    } while ( (myNum1 % 10) + (myNum2 % 10) >= 10);
       
    myAnswer = tostring(myNum1 + myNum2);
}

void MathQuestion::Ask() const
{
    const int WIDTH = 7;
    cout << setw(WIDTH) << myNum1 << endl;
    cout << "+" << setw(WIDTH-1) << myNum2 << endl;
    cout << "-------" << endl;
    cout << setw(WIDTH-myAnswer.length()) << " ";
}

bool MathQuestion::IsCorrect(const string& answer) const
{
    return myAnswer == answer;
}

string MathQuestion::Answer() const
{
    return myAnswer;
}

string MathQuestion::Description() const
{
    return "addition of two-digit numbers with NO carry";
}

CarryMathQuestion::CarryMathQuestion()
  : MathQuestion()
{
  // all done in base class constructor
}

void CarryMathQuestion::Create()
{
    RandGen gen; 
    // generate random numbers until there IS a carry
    do
    {
        myNum1 = gen.RandInt(10,49);
        myNum2 = gen.RandInt(10,49);
    } while ( (myNum1 % 10) + (myNum2 % 10) < 10);
    
    myAnswer = tostring(myNum1 + myNum2);
}

string CarryMathQuestion::Description() const
{
    return "addition of two-digit numbers with a carry";
}

HardMathQuestion::HardMathQuestion()
 : MathQuestion()
{
  // all done in base class constructor
}

void HardMathQuestion::Create()
{
    RandGen gen;
    myNum1 = gen.RandInt(100,200);
    myNum2 = gen.RandInt(100,200);
    myAnswer = tostring(myNum1 + myNum2);
}

string HardMathQuestion::Description() const
{
    return "addition of three-digit numbers";
}