lab6.cpp

/* Lab 6: Voting - An election system
 * File: lab6_skeleton.cpp
 */

#include<iostream>
using namespace std;

const int MAX_SIZE = 50;
const int MAX_STRING_LENGTH = 20;

// structure definition of Participant 
struct Participant
{
   int id;
   char name[MAX_STRING_LENGTH];
   bool hasVoted; // true if voter has voted, false otherwise
   int numVotes; // number of votes received (if the participant is a candidate
};

// structure definition of Election
struct Election
{
   Participant participants[MAX_SIZE];
   int numCandidates;
   int numVoters;
   // the candidates will occupy the first numCandidates elements in the participants array, 
   // while the other voters will occupy the next numVoters elements in the participants array
};

/* Print the list of candidates
 * Parameter:
 *    - election: the Election struct object
 */
void printCandidates(const Election &election)
{
   cout << "The list of candidates: " << endl; 
   for (int i=0; i<election.numCandidates; i++)
       cout << "Candidate id: " << election.participants[i].id << "\tName:" << election.participants[i].name << endl; 
}

/* Setup the election 
 * - initialize all the member variables of the Election object
 * Parameters:
 *    - election: a Election struct object
 * Note: 
 *    - id for voter/candidate has to be unique
 *    - initialize all the member variables of the Participant elements
 */
void setup(Election &election)
{
    cout << "Enter the details of the candidates: " << endl;
    for (int i = 0; i < election.numCandidates; ++i) {
        Participant p;
        cout << "Candidate No. " << i + 1 << endl;
        cout << "\tEnter his/her id: ";
        cin >> p.id;
        cout << "\tEnter Name: ";
        cin >> p.name;
        p.hasVoted = false;
        p.numVotes = 0;
        election.participants[i] = p;
    }

    cout << "Enter the details of the voters: " << endl;
    for (int i = 0; i < election.numVoters; ++i) {
        Participant p;
        cout << "Voter No. " << (i + 1) + election.numCandidates << endl;
        cout << "\tEnter his/her id: ";
        cin >> p.id;
        cout << "\tEnter Name: ";
        cin >> p.name;
        p.hasVoted = false;
        p.numVotes = 0;
        election.participants[i + election.numCandidates] = p;
    }
}

/* Casting votes to some candidates by a specific voter given the voter id
 * Parameters:
 *    - election: the Election struct object
 *    - voterId: the voter's id
 *    - numVotes: the number of votes the voter wants to cast
 * Note:
 *    validates the following 
 *    - voter id has to be existed
 *    - candidate id has to be existed
 */
void voting(Election& election, int voterId, int numVotes)
{
    bool foundVoter = false;
    for (Participant& p : election.participants) {
        if (p.id == voterId) {
            p.hasVoted = foundVoter = true;
            break;
        }
    }
    if (!foundVoter) {
        cout << "Voter does not exist" << endl;
        return;
    }
    for (int i = 1; i <= numVotes; ++i) {
        cout << "Enter the candidate id you want to vote for: ";
        int targetId;
        cin >> targetId;
        bool foundTarget = false;
        for (int i = 0; i < election.numCandidates; ++i) {
            if (election.participants[i].id == targetId) {
                ++election.participants[i].numVotes;
                foundTarget = true;
                break;
            }
        }
        if (!foundTarget) {
            cout << "Candidate not found" << endl;
            return;
        }
        cout << "Vote " << i << " done." << endl;
    }
}

/* Output the number of votes for each candidate
 * and announce the winner by finding who has the maximum number of votes 
 * Parameters:
 *    - election: the Election struct object
 * Note: if there is more than 1 candidate has the same number of maximum votes, 
 * announce it as a tie election.
 */
void resultTallying(const Election &election)
{
    unsigned int totalVotes = 0;
    int maxVotes = 0;
    Participant winner = election.participants[0];
    for (int i = 0; i < election.numCandidates; ++i) {
        const Participant& p = election.participants[i];
        cout << "The total number of votes for candidate " << p.id;
        cout << ": " << p.numVotes << endl;
        totalVotes += p.numVotes;
        if (p.numVotes > maxVotes) {
            maxVotes = p.numVotes;
            winner = p;
        }
    }
    cout << "The total number of votes for the whole election: " << totalVotes << endl;
    cout << "The winner is: " << winner.id << endl;
}

// Main function for the election system
int main()
{
   // Create an election
   Election election;

   cout << "===============================" << endl;
   cout << " Welcome to the voting system! " << endl;
   cout << "===============================" << endl;
   cout << "Preparing ... " << endl;
   do {
      cout << "Enter how many candidates will run for the election: \n";
      cin >> election.numCandidates;
      cout << "Enter how many more voters: \n";
      cin >> election.numVoters;
   } while (((election.numCandidates + election.numVoters) > MAX_SIZE) || (election.numCandidates <= 0));
   cout << "\n";

   // the setup phase
   setup(election);

   int currentId;
   int numVotes = 0;
   // the voting phase
   cout << "Voting starts ..." << endl;
   printCandidates(election);

   char cmd;
   //for (int i = 0; i < (election.numCandidates + election.numVoters); i++)
   do {
      cout << "Enter the voter id to start voting:\n";
      cin >> currentId;

      do {
         cout << "Enter the number of votes to be cast (<" << election.numCandidates+1 << ") :\n";
         cin >> numVotes;
      } while (numVotes > election.numCandidates);

      voting(election, currentId, numVotes);

      cout << "Continue with the next voter? (y/n) ";
      cin >> cmd;
   } while ((cmd == 'y') || (cmd == 'Y'));

   cout << "Tallying votes ..." << endl;
   //the result-tallying phase
   resultTallying(election);

   cout << "End of the election!" << endl;
   return 0;
}