Remove String from Queue of Strings

[GosanKai]

I have been stuck on this for about a week and can't seem to find an answer. I need to remove a string that is typed in by a user (command prompt) from a queue of strings (which have all been added by a user).

Here's what I have:

definition

string Game::remove(string playerName)
{
	string result;
	GameNode * pCrtNode;
	pCrtNode = new GameNode;
	(*pCrtNode).player.name=playerName;
	if(pLastToPlay==NULL)
	{
		result =  "There is no one playing.\n";
	}
	else
	{
		GameNode * pTemp = (*pCrtNode).pPrev;
		pCrtNode = (*pCrtNode).pNext;
		(*pCrtNode).pPrev = pTemp;
						
		result = playerName + " has been removed.";
	}
	
	return result;
}

declaration

string remove(string playerName);


Entire code from my four files:

--Player.h--

#pragma once

#include <string>
using namespace std;


class Player
{
public:
	string name;
};

Game.h

#pragma once

#include "Player.h"
#include <string>
using namespace std;


class Game;

class GameNode
{
private:
	friend class Game;
	Player player;
	GameNode * pNext;
	GameNode * pPrev;
};



class Game
{

public:

	Game(){pLastToPlay=NULL; pNextToPlay=NULL;}
	~Game(){}

	string transducer(string & command);
	string add(string playerName);
	string remove(string playerName);
	string play();
	string playround();



private:
	
	GameNode * pLastToPlay;
	GameNode * pNextToPlay;

};

//#endif 

Game.cpp

#include "Game.h"



string Game::transducer(string & command)
{
	string result;
	if(command=="HELP")
	{
		result="The following commands are available:\n";
		result+="\tADD <player>\n";
		result+="\tREMOVE <player>\n";
		result+="\tPLAY\n";
		result+="\tPLAYROUND\n";
		result+="\tHELP\n";
		result+="\tQUIT\n";
	}
	else if(command=="QUIT")
	{
		result="Goodbye";
	}
	else if(command.substr(0,3)=="ADD")
	{
		string param = command.substr(4,9999);
		result=add(param);
	}
	else if(command.substr(0,6)=="REMOVE")
	{
		string param = command.substr(7,9999);
		result=remove(param);
	}
	else if(command=="PLAY")
	{
		result=play();
	}
	else if(command=="PLAYROUND")
	{
		result=playround();
	}
	else
	{
		result="ERROR: The command <" + command + "> is not recognized.";
	}
	return result;
}


string Game::add(string playerName)
{
	string result;
	GameNode * pNewNode;
	pNewNode= new GameNode;
	(*pNewNode).player.name=playerName;
	if(pLastToPlay==NULL)
	{
		(*pNewNode).pNext=pNewNode;
		pLastToPlay=pNewNode;
	}
	else
	{
		(*pNewNode).pNext = (*pLastToPlay).pNext;
		(*pLastToPlay).pNext = pNewNode;
	}
	result = playerName + " has been added.";
	return result;
}

string Game::remove(string playerName)
{
	string result;
	GameNode * pCrtNode;
	pCrtNode = new GameNode;
	(*pCrtNode).player.name=playerName;
	
	if(pLastToPlay==NULL)
	{
		result =  "There is no one playing.\n";
	}
	else
	{
		//TENTH TRY
		//I give up

		//NINTH TRY
		//Several attempts changing around the code, none worked
		//pNextToPlay = pCrtNode;
		//pNextToPlay = (*pCrtNode).pNext;
		//pLastToPlay = (*pCrtNode).pPrev;
		//(*pNextToPlay).pPrev = pLastToPlay;
		//(*pLastToPlay).pNext = pNextToPlay;
				
		//EIGHT TRY
		//pNextToPlay = (*pCrtNode).pNext;
		//pLastToPlay = (*pCrtNode).pPrev;
		//pCrtNode = pLastToPlay;
		
		//SEVENTH TRY
		//pCrtNode = (*pCrtNode).pPrev;
		//(*pLastToPlay).pNext = (*pCrtNode).pNext;

		//SIXTH TRY
		//pCrtNode = (*pCrtNode).pNext;
		//(*pLastToPlay).pNext = (*pCrtNode).pNext;
		
		//FIFTH TRY
		//REMOVES THE FIRST PLAYER TO PLAY
		pCrtNode = (*pLastToPlay).pNext;
		(*pLastToPlay).pNext = (*pCrtNode).pNext;
		
		//FIRST TRY
		//GameNode * pTemp = (*pCrtNode).pPrev;
		//pCrtNode = (*pCrtNode).pNext;
		//(*pCrtNode).pPrev = pTemp;
			
		//SECOND TRY		
		//(*pLastToPlay).pNext = (*pCrtNode).pNext;
		//pCrtNode = NULL;

		//THIRD TRY
		//pLastToPlay = pCrtNode;
		
		//FOURTH TRY
		//(*pLastToPlay).pNext = (*pCrtNode).pNext;
		//delete pCrtNode;
		
		result = playerName + " has been removed.";
	}
	
	return result;
}

string Game::play()
{
	string result;
	if(pLastToPlay==NULL)
	{
		result= "There are no Players to play.";
	}
	else
	{
		pLastToPlay=(*pLastToPlay).pNext;
		result= (*pLastToPlay).player.name + " takes a turn.";
	}
	return result;
}


string Game::playround()
{
	string result;
	GameNode * pMarker=pLastToPlay;
	do
	{
		result += play()+"\n";
	} while (pLastToPlay!=pMarker);
	return result;
}

main.cpp

//********************************************************
//
// (c) COPYRIGHT 2008 Dr. Thomas Fernandez
//         All rights reserved.
//
//********************************************************


// adding these lines lets us use cout and other things
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;

// adding this line lets us use Game.
#include "Game.h"



string getCommandFrom(ifstream & fin)
{
	string com;
	if(fin.eof())
	{
		com="ENDBATCH";
	}
	else
	{
		getline(fin,com);
	}
	if( fin.eof() && com=="" )
	{
		com="ENDBATCH";
	}
	return com;
}



void commandLineInterface(Game & g)
{
	ifstream fin;
	ofstream fout;
	bool batchActive=false;
	bool redirectActive = false;
	string com;
	cout<<g.transducer((string)"HELP")<<endl;
	do
	{
		if(!batchActive)
		{
			cout<<">";
			getline(cin,com);
		}
		else
		{
			com=getCommandFrom(fin);
		}


		//META COMMANDS
		if(com.substr(0,5)=="BATCH")
		{
			string filename=com.substr(6,9999);
			fin.open(filename.c_str());
			batchActive=true;
		}
		else if(com=="ENDBATCH")
		{
			fin.close();
			fin.clear();
			batchActive=false;
		}
		else if(com.substr(0,8)=="REDIRECT")
		{
			string filename=com.substr(9,9999);
			fout.open(filename.c_str());
			redirectActive=true;
		}
		else if(com=="DIRECT")
		{
			fout.close();
			fout.clear();
			redirectActive=false;
		}
		else
		{
			if(!redirectActive)
			{
				cout<<g.transducer(com)<<endl;
			}
			else
			{
				fout<<g.transducer(com)<<endl;
			}
		}
	} while (com != "QUIT");
}



void simpleCommandLineInterface(Game & g)
{
	string command;
	cout<<g.transducer((string)"HELP")<<endl;
	do
	{
		cout<<">";
		getline(cin,command);
		cout<<g.transducer(command)<<endl;
	} while (command != "QUIT");
}




int main()
{
	Game game;
	commandLineInterface(game);
	return 0;
}

[ne555]

string Game::remove(string playerName)
{
	string result;
	GameNode * pCrtNode;
	pCrtNode = new GameNode; //¿why?
	(*pCrtNode).player.name=playerName;
	if(pLastToPlay==NULL)
	{
		result =  "There is no one playing.\n";
	}
	else
	{
		GameNode * pTemp = (*pCrtNode).pPrev; 
		pCrtNode = (*pCrtNode).pNext; //memory leak
		(*pCrtNode).pPrev = pTemp;
						
		result = playerName + " has been removed.";
	}
	
	return result;
}

I suppose that at least you should traverse the container, ¿don't you think?
Also, it will be better that you return a bool, handling the messages outside.

Check the STL