frogwalk3.cpp

来自「C++&datastructure书籍源码,以前外教提供现在与大家共享」· C++ 代码 · 共 128 行

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

#include "prompt.h"
#include "tvector.h"
#include "randgen.h"
#include "dice.h"

class Walker;
class WalkRecorder
{
  public:
    WalkRecorder();
    void Record(const Walker& walker);
    void Print(ostream& out) const;
    
  private:
    static int MAX;
    tvector<int> myRecord;
    int          myBeyondCount;
};

class Walker
{
  public:
    Walker(WalkRecorder* wrec);

    void Walk(int steps);
    int  Position() const;
    void ChangeRecorder(WalkRecorder* wrec);

  private:
    int  myPosition;
    WalkRecorder * myRecorder;
};

int WalkRecorder::MAX = 100;

WalkRecorder::WalkRecorder()
    : myRecord(2*MAX+1,0), myBeyondCount(0)
{
    // record -MAX..MAX, all zero
}

void WalkRecorder::Record(const Walker& walker)
{
    int pos = walker.Position();
    if (fabs(pos) > MAX)
    {   myBeyondCount++;
    }
    else
    {   myRecord[pos+MAX]++;
    }
}

void WalkRecorder::Print(ostream& out) const
{
    int lowIndex=-1,highIndex=0,k;
    for(k=0; k < 2*MAX+1; k++)
    {   if (myRecord[k] != 0)
        {   if (lowIndex == -1) lowIndex = k;
	        highIndex = k;
	    }
    }
    if (lowIndex == -1)
    {   out << " no steps taken" << endl;
	    return;
    }
    for(k=lowIndex; k <= highIndex; k++)
    {   cout << k-MAX << "\t" << myRecord[k] << endl;
    }
    cout << endl << "beyond boundaries = " << myBeyondCount << endl;
}

Walker::Walker(WalkRecorder * wrec)
    : myPosition(0), myRecorder(wrec)
{
    
}

void Walker::Walk(int steps)
{
    Dice d(2);
    int k;
    for(k=0; k < steps; k++)
    {   if (d.Roll() == 1)
	    {   myPosition++;
	    }
	    else
	    {   myPosition--;
	    }
	    myRecorder->Record(*this);
    }
}

int Walker::Position() const
{
    return myPosition;
}

void Walker::ChangeRecorder(WalkRecorder* wrec)
{
    myRecorder = wrec;
}

int main()
{
    WalkRecorder * rec =  new WalkRecorder();
    WalkRecorder * rec2 = new WalkRecorder();
    Walker w1(rec);
    Walker w2(rec);
    int steps = PromptRange("how many steps ",1,10000);
    w1.Walk(steps);
    w2.Walk(steps);
    rec->Print(cout);
    
    cout << endl << "another walk" << endl << endl;
    
    w1.ChangeRecorder(rec2);
    w2.ChangeRecorder(rec2);
    w1.Walk(steps);
    w2.Walk(steps);
    rec2->Print(cout);
    return 0;
}