Linked lists and segmentation faults

[LNAM4iN6]

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

char getMenuChoice();
void verticalSpace(int);


class countyElectionResults{

  friend ostream &operator<<(ostream &, countyElectionResults);
  friend istream &operator>>(istream &, countyElectionResults &);

public:

  countyElectionResults();
  countyElectionResults(string);
  bool loadFile(string);
  string getCountyName();
  vector<char> getVotes();
  void showVotes();
  int getNullifierVotes();
  int getFielditeVotes();
  int getOtherVotes();
  int getTotalVotes();
  countyElectionResults * getNext();
  void setNext(countyElectionResults*);

private:
  string countyName;
  vector<char> votes;
  int nullifierVotes;
  int fielditeVotes;
  int otherVotes;
  void countVotes();
  countyElectionResults * next;

};

ostream &operator<<(ostream &output, countyElectionResults results){
  
  
  output << setw(25) << results.countyName 
	 << setw(15) << results.fielditeVotes
	 << setw(15) << results.nullifierVotes
	 << setw(15) << results.otherVotes;


  return output;
}

istream &operator>>(istream &input, countyElectionResults &results){


  char vote;
  getline(input, results.countyName);
   
  while (input >> vote){
    results.votes.push_back(vote);
  }
  results.countVotes();  

  return input;
}

countyElectionResults * countyElectionResults::getNext(){
	return next;
}

void countyElectionResults::setNext(countyElectionResults* nextNode){
	next = nextNode;
}

countyElectionResults::countyElectionResults(){

  nullifierVotes = 0;
  fielditeVotes = 0;
  otherVotes = 0;
  next = NULL;
 
}

countyElectionResults::countyElectionResults(string filename){

  nullifierVotes = 0;
  fielditeVotes = 0;
  otherVotes = 0;
  next = NULL;
  loadFile(filename);
}


bool countyElectionResults::loadFile(string filename){


  ifstream countyFile;
  char vote;

  countyFile.open(filename.c_str());
  if (!countyFile){
    cout << "File not found: " << filename << endl;
    return false;
  }

  // Read in the first line with the county name

  getline(countyFile, countyName);
   
  while (countyFile >> vote){
    votes.push_back(vote);
  }
  countVotes();
  
  return true;
  
}

void countyElectionResults::showVotes(){

  cout << setw(15) << countyName << endl;
  for (int i = 0; i < votes.size(); i++){
    cout << setw(15) << votes[i] << " " <<endl;
  }
}

string countyElectionResults::getCountyName(){

  return countyName;

}

vector<char> countyElectionResults::getVotes(){

  return votes;

}

int countyElectionResults::getNullifierVotes(){

  return nullifierVotes;

}
 
int countyElectionResults::getFielditeVotes(){
  return fielditeVotes;

}
 
int countyElectionResults::getOtherVotes(){

  return otherVotes;

}


int countyElectionResults::getTotalVotes(){

  return votes.size();

}

void countyElectionResults::countVotes(){
  
  nullifierVotes = 0;
  fielditeVotes = 0;
  otherVotes = 0;

  for (int i = 0; i < votes.size(); i ++){
    switch (votes[i]){
    case 'N':
    case 'n':
      nullifierVotes ++;
      break;
    case 'F':
    case 'f':
      fielditeVotes ++;
      break;
    default:
      otherVotes ++;      
    }

  }

}

class countyElectionList{

public:
  countyElectionList();
  countyElectionResults at(int);
  void push_back(countyElectionResults *);
  int size();
  bool empty();

private:
  countyElectionResults * head;
  int elementCount;

};

// A constructor that initializes the private data members
countyElectionList::countyElectionList(){
	countyElectionList::head = NULL;
}

// This returns the countyElectionResults result at a particular point
// in the list.
// This is analogous to the at method in the vector class.
countyElectionResults countyElectionList::at(int place){
  countyElectionResults * current = head;
  while (current != NULL){
      if (place==current->getNullifierVotes()){
      return *current;
  }
  current = current->getNext();
  }
}





// This method adds a countyElectionResults object to the end of the list.
// It is analogous to the push_back method in the vector class.
void countyElectionList::push_back(countyElectionResults * newCER){

if(head == NULL)
	head = newCER;
	else
		{
		countyElectionResults * current = head;
		while(current->getNext() != NULL){
			current = current->getNext();
		}
	current->setNext(newCER);
	}

}


// This method returns the number of elements on the list.
// It is analogous to the size method in the vector class
int countyElectionList::size(){
    int count = 0;

  countyElectionResults * current = head;
  while (current != NULL){
      count ++;
      current = current->getNext();
  }

  return count;

  
}


//This method returns true if the list has no elements
// It is analogous to the empty method in the vector class.
bool countyElectionList::empty(){
  return head == NULL;

}



class stateElectionResults {

public:
  void addCountyFile();
  void showAllCountyResults();
  void showCountyResults(string);
  void showCountyVotes(string);
  void listCounties();
    

private:
 countyElectionList stateResults;

};



void stateElectionResults::addCountyFile(){

  string countyFileName;
  int voteCount = 0;

  cout << "Please enter the county file name to add:";
  getline(cin, countyFileName);
  
  countyElectionResults *  newResults = new (countyElectionResults);
  if (newResults->loadFile(countyFileName)){
    stateResults.push_back(newResults);
  }
 
}

void stateElectionResults::showAllCountyResults(){

  int nullifierVotes = 0;
  int fielditeVotes = 0;
  int otherVotes = 0;

  verticalSpace(5);
  cout << setw(25) << "County Name"
       << setw(15) << "Fieldite Votes" 
       << setw(15) << "Nullifier Votes" 
       << setw(15) << "Other Votes" 
       << endl;

  for (int i = 0; i < stateResults.size(); i++){

    cout << stateResults.at(i) << endl;
    
    nullifierVotes +=  stateResults.at(i).getNullifierVotes();
    fielditeVotes +=  stateResults.at(i).getFielditeVotes();
    otherVotes +=  stateResults.at(i).getOtherVotes();
  }

  cout << setw(25) << "Total:"
       << setw(15) << fielditeVotes
       << setw(15) << nullifierVotes
       << setw(15) << otherVotes
       << endl;    
  verticalSpace(5);
}

void stateElectionResults::showCountyResults(string countyName){

  verticalSpace(5);
  for (int i = 0; i < stateResults.size(); i++){
  
    if (stateResults.at(i).getCountyName() == countyName){
      cout << stateResults.at(i) << endl;
      break;
    }
  }
  verticalSpace(5);
}

void stateElectionResults::showCountyVotes(string countyName){

    for (int i = 0; i < stateResults.size(); i++){
   
      if (stateResults.at(i).getCountyName() == countyName){
	stateResults.at(i).showVotes();
	break;
      }
    }
}

void stateElectionResults::listCounties(){

  cout << setw(25) << "COUNTIES" << endl;    
  for (int i = 0; i < stateResults.size(); i++){
    cout << setw(25) << stateResults.at(i).getCountyName() << endl;    
  }

}


int main(){

  stateElectionResults theResults;
  bool done = false;
  char choice;
  string county;

  do {

    choice = getMenuChoice();
    switch (choice){
    case 'Q':
    case 'q':
      done = true;
      break;
    case 'A':
    case 'a':
      theResults.addCountyFile();
      break;
    case 'R':
    case 'r':
      theResults.showAllCountyResults();
      break;
    case 'L':
    case 'l':
      theResults.listCounties();
      break;
    case 'C':
    case 'c':
      cout << "Please enter the county name: ";
      getline(cin,county);
      theResults.showCountyResults(county);
      break;
    case 'V':
    case 'v':
      cout << "Please enter the county name: ";
      getline(cin,county);
      theResults.showCountyVotes(county);
      break;
    default:
      cout << "Unknown choice. Please try again" << endl;
    }
    

  } while (!done);
}

void verticalSpace(int space){

  for (int i = 0; i < space; i++){
    cout << endl;
  }

}

char getMenuChoice(){

  char choice;
  verticalSpace(5);
  cout << setw(45) << "A: Add a county file" << endl;
  cout << setw(45) << "L: List counties" << endl;
  cout << setw(45) << "R: show all results" << endl;
  cout << setw(45) << "C: show single county result" << endl;
  cout << setw(45) << "V: verify single county votes" << endl;
  cout << setw(45) << "Q: quit" << endl;
  
  cout << "Your choice: ";
  cin >> choice;
  string trash;
  getline (cin,trash);
  verticalSpace(5);
  return choice;
  
}

[LNAM4iN6]

I am struggling with linked lists and how to fix segmentation faults for the code above.

The assignment is that I need to write a code that reads an indeterminate amount of files full of voting information and outputs certain aspects of these files with respect to the user input. However, I must use linked lists instead of vectors aside from one vector that is full of the votes read.
The text files will come in the form of:

County
n
f
f
n
v
etc.

Where county is the county name and the letters are the votes cast.

I am almost certain the problem lies in one of three methods.

212 countyElectionResults countyElectionList::at(int place){ ((I am having trouble with this method regardless of whether the segmentation fault stems from this. How exactly do I return all of the results rather than just one party?))

246 int countyElectionList::size(){

OR 263 bool countyElectionList::empty(){
I am so sorry for the long post, but I wanted to be as thorough as possible. The segmentation fault occurs whenever the user enters L, R, C, or V. Thank you in advance!

[LNAM4iN6]

I have deduced that the problem may lie in

countyElectionResults countyElectionList::at(int place){
  countyElectionResults * current = head;
  while (current != NULL){
      if (place==current->getNullifierVotes()){
      return *current;
  }
  current = current->getNext();
  }
}

but I am not quite sure how to fix the problem that would occur if place is not found on the list. Any suggestions?

[cire]

Return a pointer?

If the idea is to return the 'nth' element of the list, the code for at should probably be more along the lines of:

countyElectionResults countyElectionList::at(int place){
  unsigned count = 0 ;
  countyElectionResults * current = head;

  while (count < place && current->getNext() ){
      ++count ;
      current = current->getNext();
  }

  return *current ;
}

That just returns the last element if place happens to exceed the size of the list.

[Edit: By the way, memory allocated with new should be delete'd at some point. You should probably also look into when it might be appropriate to define a destructor, copy constructor and copy assignment operator.]

[LNAM4iN6]

Ah that makes so much more sense! Thank you for the explanation!