qvisty/runoff-cs50

#include <stdio.h>
#include <string.h>

// Max voters and candidates
#define MAX_VOTERS 100
#define MAX_CANDIDATES 9

// preferences[i][j] is jth preference for voter i
int preferences[MAX_VOTERS][MAX_CANDIDATES];

typedef enum {false, true}bool;

// Candidates have name, vote count, eliminated status
typedef struct
{
    char name[100];
    int votes;
    bool eliminated;
}
candidate;

// Array of candidates
candidate candidates[MAX_CANDIDATES];

// Numbers of voters and candidates
int voter_count;
int candidate_count;

// Function prototypes
bool vote(int voter, int rank, char name[]);
void tabulate(void);
bool print_winner(void);
int find_min(void);
bool is_tie(int min);
void eliminate(int min);

//--------------------------------------------------------------------------------------------------------------------------------------

int main(int argc, char *argv[])
{
    // Check for invalid usage
    if (argc < 2)
    {
        printf("Usage: runoff [candidate ...]\n");
        return 1;
    }

    // Populate array of candidates
    candidate_count = argc - 1; //minus one = -./name of file
    if (candidate_count > MAX_CANDIDATES)
    {
        printf("Maximum number of candidates is %i\n", MAX_CANDIDATES);
        return 2;
    }
    for (int i = 0; i < candidate_count; i++)
    {
        strcpy(candidates[i].name, argv[i + 1]);
        candidates[i].votes = 0;
        candidates[i].eliminated = false;
    }

    printf("Number of voters: ");
    scanf("%d", &voter_count);

    if (voter_count > MAX_VOTERS)
    {
        printf("Maximum number of voters is %i\n", MAX_VOTERS);
        return 3;
    }

    // Keep querying for votes
    for (int i = 0; i < voter_count; i++)
    {
        // Query for each rank
        for (int j = 0; j < candidate_count; j++)
        {
            char name[100];
            printf("Rank %i: ", j + 1);
            scanf("%s", name);

            // Record vote, unless it's invalid
            if (!vote(i, j, name))
            {
                printf("Invalid vote.\n");
                return 4;
            }
        }
        printf("\n");
    }

    // Keep holding runoffs until winner exists
    while (true)
    {
        // Calculate votes given remaining candidates
        tabulate();

        // Check if election has been won
        bool won = print_winner();
        if (won)
        {
            break; //if there is a winner, break out of loop
        }

        // Eliminate last-place candidates
        int min = find_min();
        bool tie = is_tie(min);

        // If tie, everyone wins
        if (tie)
        {
            for (int i = 0; i < candidate_count; i++)
            {
                if (!candidates[i].eliminated)
                {
                    printf("%s\n", candidates[i].name);
                }
            }
            break;
        }

        // Eliminate anyone with minimum number of votes
        eliminate(min);

        // Reset vote counts back to zero
        for (int i = 0; i < candidate_count; i++)
        {
            candidates[i].votes = 0;
        }
    }
    return 0;
}

//------------------------------------------------------------------------------------------------------------------

// Record preference if vote is valid
bool vote(int voter, int rank, char name[])
{

    int check = 0;
    for (int i = 0; i < candidate_count; i++)
    {
        if (strcmp(name, candidates[i].name) == 0)
        {
            preferences[voter][rank] = i;
        }
        else
            check++;
    }

    if (check == candidate_count)
        return false;
    else
        return true;

}

// Tabulate votes for non-eliminated candidates
void tabulate(void)
{
    for (int i =0; i < voter_count; i++)
    {
        if (candidates[preferences[i][0]].eliminated == false)
            candidates[preferences[i][0]].votes++;
        else //loop through candidates whose status is still not false.
        {
            int j = 0;
            do
            {
                j++;
            }
            while (candidates[preferences[i][j]].eliminated == true);
            candidates[preferences[i][j]].votes++;
        }
    }
    return;
}

// Print the winner of the election, if there is one
bool print_winner(void)
{
    //int check = 0;
    for (int i = 0; i < voter_count; i++)
        {
            if (candidates[i].votes >= (voter_count/2)+1)
                {
                    printf("Winner: %s", candidates[i].name);
                    return true;
                }
        }
        return false;
}

// Return the minimum number of votes any remaining candidate has
int find_min(void)
{
    int findmin = voter_count;
    for (int i = 0; i < candidate_count; i++)
    {
        if (findmin > candidates[i].votes)
            {
                if (candidates[i].eliminated == false)
                    findmin = candidates[i].votes;
            }
    }
    //return number of min vote
    return findmin;
}

// Return true if the election is tied between all candidates, false otherwise
bool is_tie(int min)
{
    for (int i = 0; i < candidate_count; i++)
    {
        if (candidates[i].eliminated == false)
        {
            if (candidates[i].votes != min)
            {
                return false;
            }
        }
    }
    return true;
}

// Eliminate the candidate (or candidiates) in last place
void eliminate(int min)
{
    for (int i = 0; i < candidate_count; i++)
    {
        if (candidates[i].votes == min)
        {
            candidates[i].eliminated = true;
        }
    }
    return;
}