Am I using dynamic arrays correctly?

Question

New programmer here. I need to write a program using dynamic arrays to simulate an election. The program should first ask for a number of candidates, then take the candidate names and the number of votes received. Lastly, find the winner and print out the results.

I want to see if I've used the dynamic arrays correctly, and in what ways my code could be improved. I feel like I used a few too many for loops here. When I previously wrote this program, I created a candidate class to store each name and vote, however I do not believe you are able to create an object when using a dynamic array.

Any feedback or better insight on how to better use dynamic arrays is appreciated!

#include <iostream>
using namespace std;

void electionResults(double *votes, string *names, int candidates)
{
    double total_votes;
    int max = 0;
    int winner;
    // double Percentage[canidates];

    // counts the total number of votes
    for (int i = 0; i < candidates; i++)
    {
        total_votes += votes[i];
    }

    // determines who has the most votes
    for (int i = 0; i < candidates; i++)
    {
        if (votes[i] > max)
        {
            max = votes[i];
            winner = i;
        }
    }

    // prints results
    cout << "Result of the Election********" << endl;
    cout << "Name of Candidate"
         << "\t"
         << "Votes Received"
         << "\t"
         << "Percentage" << endl;
    for (int i = 0; i < candidates; i++)
    {
        cout << names[i] << "\t\t\t";
        cout << votes[i] << "\t\t";
        cout << (votes[i] * 100) / total_votes << "%" << endl;
    }

    cout << "Total Votes: " << total_votes << "\n";
    for (int i = 0; i < candidates; i++)
    {
        if (winner == i)
        {
            cout << "The winner is " << names[i] << "\n";
        }
    }
}

int main()
{
    string name;
    double votes;
    int Num_candidates;
    // dynamic array declerations
    double *voting_Array;
    string *name_Array;

    cout << "Enter the number of candidates\n";
    cin >> Num_candidates;

    voting_Array = new double[Num_candidates];
    name_Array = new string[Num_candidates];

    for (int i = 0; i < Num_candidates; i++)
    {
        cout << "Enter candidate's " << i + 1 << " last name \n";
        cin >> name;
        name_Array[i] = name;
    }

    for (int i = 0; i < Num_candidates; i++)
    {
        cout << "Enter votes for " << name_Array[i] << " ";
        cin >> votes;
        voting_Array[i] = votes;
    }

    electionResults(voting_Array, name_Array, Num_candidates);

    voting_Array = NULL;
    name_Array = NULL;
    return 0;
}       

Answer 1

There are some issues with your electionResults() function.

double total_votes; is an uninitialized variable, so total_votes += votes[i]; afterwards is undefined beehvior. Same with int winner;

Also, since votes is an array of doubles, max should also be a double, not an int. But then, can you really have fractions of a vote? Perhaps votes should be an array of ints instead?

That being said, your use of dynamic arrays is almost correct. You are creating, filling, and displaying the arrays correctly, but where you are going wrong is freeing the arrays. Since the arrays are allocated with new[], you need to use delete[] to free them, eg:

voting_Array = new double[Num_candidates];
name_Array = new string[Num_candidates];
...
delete[] voting_Array;
delete[] name_Array;

Though, you really should be using std::vector insted of new[]/delete[] directly. Let vector handle the dynamic memory for you.

And yes, you can create objects in arrays.

Try something more like this:

#include <iostream>
#include <vector>
#include <limits>
using namespace std;

struct Candidate
{
    string name;
    double/*unsigned int*/ votes;
}

void electionResults(const vector<Candidate> &candidates)
{
    // count the total number of votes and
    // determine who has the most votes

    double/*unsigned int*/ total_votes = candidates[0].votes;
    double/*unsigned int*/ max_votes = candidates[0].votes;
    size_t winner = 0;

    for (size_t i = 1; i < candidates.size(); ++i)
    {
        total_votes += candidates[i].votes;

        if (candidates[i].votes > max_votes)
        {
            max_votes = candidates[i].votes;
            winner = i;
        }
    }

    // prints results
    cout << "Result of the Election********" << endl;
    cout << "Name of Candidate"
         << "\t"
         << "Votes Received"
         << "\t"
         << "Percentage" << endl;
    for (size_t i = 0; i < candidates.size(); ++i)
    {
        cout << candidates[i].name << "\t\t\t";
        cout << candidates[i].votes << "\t\t";
        cout << (double(candidates[i].votes) * 100.0 / total votes) << "%" << endl;
    }

    cout << "Total Votes: " << total_votes << "\n";
    cout << "The winner is " << candidates[winner].name << "\n";
}

int main()
{
    size_t Num_candidates;

    do
    {
        cout << "Enter the number of candidates\n";

        if (cin >> Num_candidates)
        {
            if (Num_candidates > 0)
                break;

            cout << "At least 1 candidate is needed!\n";
        }
        else
        {
            cin.clear();
            cin.ignore(numeric_limits<streamsize>::max(), '\n');
            cout << "Invalid number entered!\n";
        }
    }
    while (true);

    vector<candidate> voting_Array(Num_candidates);

    for (size_t i = 0; i < Num_candidates; ++i)
    {
        cout << "Enter candidate's " << i + 1 << " last name \n";
        cin >> voting_Array[i].name;
    }

    for (size_t i = 0; i < Num_candidates; ++i)
    {
        do
        {
            cout << "Enter votes for " << voting_Array[i].name << " ";

            if (cin >> voting_Array[i].votes)
            {
                if (voting_Array[i].votes >= 0)
                    break;

                cout << "Votes cant be negative!\n";
            }
            else
            {
                cin.clear();
                cin.ignore(numeric_limits<streamsize>::max(), '\n');
                cout << "Invalid number entered!\n";
            }
        }
        while (true);
    }

    electionResults(voting_Array);

    return 0;
}