Thread: Mastermind program problem with iterator

Hello, I'm writing a mastermind program in c++. In mastermind you guess a 4 digitcode and the computer gives two answers after each guess:
Gold: Right digit in the right place
Silver: The digit is in the code but it the wrong place

The program runs and the actual game works fine but there should also be a top 10 highscorelist. And here i get a problem when i want to erase the 11th score and then save it too a file. I get an error that the iterator is not incrementable.

Any ideas?
P.S I've written some comments to show what the program does and where it goes wrong.

Code:

#include <iostream>
#include <string>
#include <list>
#include <fstream>
#include <conio.h>
#include <ctime>
#include <string>
using namespace std;
struct Person
{
	string name;
	string tries;
};
void play(list<Person>& lista);
void highscore(list<Person> lista);
int main()
{
	Person person; 
	list<Person> lista;
	ifstream inFil; //loads highscorelist
	inFil.open("C:\\Documents and Settings\\Philip\\Skrivbord\\Läxor\\Highscore.txt");
    if(!inFil)
    {
       cout << "Highscorefile can't be opened";
       exit(1);
    }
	while(getline(inFil, person.name))
		lista.push_back(person);
	inFil.close();
	int menu;
	cout <<" ============================  1. PLAY  ============================ \n";
	cout <<" ==========================  2. Highscores ========================= \n  ";
	cin >> menu;
	if(menu==1) //choice between playing and looking at the highscore
		play(lista);
	if(menu==2)
		highscore(lista);
	cin.ignore();
	getchar();
	return(0);
}
 
 
 
void play(list<Person>& lista)
{
	Person person;
	int answer[4], guess[4], copyanswer[4], i, gold=0, silver=0, a=0, k=0, j=0;
	srand(time(NULL));
	for(i=0; i<4; i++)
	 answer[i]=rand()%9+1; // randomises the answer
	while(gold!=4)
	{
		for(i=0; i<4; i++)
			cout << answer[i]; //cheat for now to see the answer
 
		silver=0;
		k=0;
		gold=0;
		a=a+1;
 
 
 
		cout << "========== Try " << a << "======== " << endl;
		cout << "Type in your guess, seperate each number with a space: ";
		cin >> guess[0] >> guess[1] >> guess[2] >> guess[3]; //spara gissning
 
  for(i=0 ; i<4 ; i++)
   copyanswer[i] = answer[i];
 
  // everything gets changed to 13 so the same digit doesn't get 2 hits
  for(i=0; i<4; i++)
  {
   if(copyanswer[i]==guess[i]) //check for gold
   {gold=gold+1;
    copyanswer[i] = 13;
  }
  }
 
  for(i=0; i<4; i++)  //check for silver
  {
   for(j=0; j<4; j++)
   {
    if(copyanswer[i]==guess[j])
    {
    silver=silver+1;
    guess[j]= 13;
    copyanswer[i] =13;
    }
   }
  }
 
		if(gold==4)
		{
			cout << "CONANANAGRATAS YOU WERE CORRECT!!!!!" << endl;
			cin.ignore();
		}
		else
		{	cout << " Gold = " << gold << " and silver = " << silver <<  endl;
			cin.ignore();
		}
	}
		cout << "Maybe you have reached the highscore, please type in your name: "; // Gets names into the highscore list
		getline(cin, person.name);
		person.tries=a;
		lista.push_back(person);
		list <Person>::iterator it=lista.begin()++; //sorts the list after number of tries
		list <Person>::iterator it2=lista.begin();
		while(it!=lista.end())
		{
			it2=lista.begin();
			while(it2!=it && (*it2).tries < (*it).tries)
			{
				it2++;
			}
			lista.insert(it2,*it);
			lista.erase(it++);
 
		} 
 
		for(int c = 1; c < 11; c++)  //HERE SOMETHING GOES WRONG!!!
		{ 
			it++;
		}
 lista.erase(it); //should always be 10 highscores before the program starts
	ofstream utFil; 
	utFil.open("C:\\Documents and Settings\\Philip\\Skrivbord\\Läxor\\Highscore.txt"); //saves the highscorelist
	if(!utFil)
   {
      cout << "Highscore file can't be opened";
      exit(1);
   }
   for(it = lista.begin(); it != lista.end(); it++)
      utFil << (*it).name << '\t' << (*it).tries << endl;
   utFil.close();
 
 
}
void highscore(list<Person> lista)
{
	Person person;
	int a=1;
	cout << " ================ HIGHSCORE ============== ";
	cout << "\n Lista:\n";
   list<Person>::iterator it;
   for(it = lista.begin(); it !=lista.end(); it++)
   {
		cout << a << '\t' << (*it).name << '\t' << (*it).tries << endl;
		a=a+1;
   }
   cin.ignore();
}

When the while loop ends, it will be, by definition, lista.end(). And the end of a container is not incrementable (since it is, well, the end of the container).

(I mean the while loop directly above where you try to move forward 10 times.)

(And when you put a new score in the list, don't you want to delete the bottom, not the person who was in the spot you just earned?)

You are erasing whatever the iterator "it" is pointing at, making "it" a null pointer, and then you try to use it. At least that's what it seems, but it's kinda hard to read through all that. Please use proper identation when you post code.

Also, that way of saving scores is limited to 10, and confusing. Why don't you just load all the scores from a file, store them in a vector, update the vector after you play the game, sort it, and then save it? That way you would just check the size of the vector and it would work for everything.