Thread: Josephus problem variant logic troubles

I'm supposed to implement a variant of the josephus problem for my C++ class using an STL list. I've got it pretty much half working but there is a logic oversight that I'm making and I keep getting assertion errors. The problem is, I believe, 'wrapping' the iterator from the end of the list to the beginning when the tempcount is less than the M value - or at least that's what the visual studio debugger would lead me to believe. In that instance, itr seems to be pointing to garbage. Help!

Code:

    #include <iostream>
    #include <list>

    using namespace std;

    int main(){
       //M: incrememnt amount
       //N: size of list/number of current 'persons'
       //playerList<int>: our list, numbered 1 to N
       //done: becoems true when current persons is 1
       
       bool done = false;

       int N = 0;
       int M = 0;

       cout <<"Please enter # of 'players': ";
       cin >> N;

       cout <<"\nPlease enter an incriment value: ";
       cin >> M;

       //check for default case, if there's only a single 'player'
       if(N <= 1){
          cout <<" We need more players!";
          system("PAUSE");
          return 0;
       }

       //so we have our values, lets create our list to spec
       list<int> playerList;
       for(int i = 0; i < N; i++){
          playerList.push_back(i+1);
       }


       //iterator
       list<int>::iterator itr;
       itr = playerList.begin();


       int tempCount = 1;

       //add offset(M) to the iterator starting at begin(gradually). whatever it lands on is erased.
       //continue this , and wrap around if iterator == end
       while(done == false){
          if(N == 1){
             done = true;
             cout << "\nWinner: Player" << *itr << endl; //outputs what the iterator is pointing at 
          }
          else{
             //okay, so now we start to traverse the list
             
             //do we wrap?
             //and we have tempcount to add to the iterator until we reach m
             if(itr == playerList.end()){
                if(tempCount == M){
                   //temp = true;
                   tempCount = 0;
                   N--;
                   cout << "\n Player " << *itr << " lost.";
                   itr = playerList.erase(itr);
                
                }
                else{
                   itr = playerList.begin(); //almost the same as itr++
                   tempCount++;
                }
             }

             
             else{
                //we didn't wrap, what do we do
                //1: increment the iterator//tempcount
                //2: if tempCount = M, delete whats at the iterator
                //2.1: if we delete, reset tempCount, and decrease N, output result
                //3: soemthing

                if(tempCount == M){
                   tempCount = 0;
                   N--;
                   cout << "\n Player " << *itr << " lost.";
                   itr = playerList.erase(itr);
                   
                }
                else{
                   if(itr == playerList.end()){
                      itr = playerList.begin(); //almost the same as itr++
                      tempCount++;
                   }
                   else{
                      itr++;
                      tempCount++;
                   }
                }
                
             }//end inside else
          }//end else
       }//end while

       system("PAUSE");

       return 0;
    }