Tideman Completion

tideman.c

#include <cs50.h>
#include <stdio.h>
#include <string.h>

// Max number of candidates
#define MAX 9

// preferences[i][j] is number of voters who prefer i over j
int preferences[MAX][MAX];

// locked[i][j] means i is locked in over j
bool locked[MAX][MAX];

// Each pair has a winner, loser
typedef struct
{
    int winner;
    int loser;
} pair;

// Array of candidates
string candidates[MAX];
pair pairs[MAX * (MAX - 1) / 2];

int pair_count = 0;
int candidate_count = 0;

// Function prototypes
bool vote(int rank, string name, int ranks[]);
void record_preferences(int ranks[]);
void add_pairs(void);
void sort_pairs(void);
void lock_pairs(void);
void print_winner(void);

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

    // Populate array of candidates
    candidate_count = argc - 1;
    if (candidate_count > MAX)
    {
        printf("Maximum number of candidates is %i\n", MAX);
        return 2;
    }
    for (int i = 0; i < candidate_count; i++)
    {
        candidates[i] = argv[i + 1];
    }

    // Clear graph of locked in pairs
    for (int i = 0; i < candidate_count; i++)
    {
        for (int j = 0; j < candidate_count; j++)
        {
            locked[i][j] = false;
        }
    }

    pair_count = 0;
    int voter_count = get_int("Number of voters: ");

    // Query for votes
    for (int i = 0; i < voter_count; i++)
    {
        // ranks[i] is voter's ith preference
        int ranks[candidate_count];

        // Query for each rank
        for (int j = 0; j < candidate_count; j++)
        {
            string name = get_string("Rank %i: ", j + 1);

            if (!vote(j, name, ranks))
            {
                printf("Invalid vote.\n");
                return 3;
            }
        }

        record_preferences(ranks);

        printf("\n");
    }

    add_pairs();
    sort_pairs();
    lock_pairs();
    print_winner();
    return 0;
}

// Update ranks given a new vote
bool vote(int rank, string name, int ranks[])
{

    for (int i = 0; i < candidate_count; i++)
    {
        if (strcmp(name, candidates[i]) == 0)
        {
            ranks[rank] = i;
            return true;
        }
    }
    return false;
}

// Update preferences given one voter's ranks
void record_preferences(int ranks[])
{
    // preferences[i][j] is number of voters who prefer i over j

    int count = 1;
    for (int i = 0; i < candidate_count - 1; i++)
    {
        for (int j = count; j < candidate_count; j++)
        {
            preferences[ranks[i]][ranks[j]] = (preferences[ranks[i]][ranks[j]] + 1);
            // printf("Adds %i ")
        }
        count = count + 1;
    }

    return;
}

// Record pairs of candidates where one is preferred over the other
void add_pairs(void)
{
    // use pair pairs
    // update global pair count
    for (int i = 0; i < candidate_count; i++)
    {
        for (int j = 0; j < candidate_count; j++)
        {
            if (preferences[i][j] > preferences[j][i])
            {
                pairs[pair_count].winner = i;
                pairs[pair_count].loser = j;
                // printf("Pair winner: %i Pair Loser %i\n",pairs[pair_count].winner, pairs[pair_count].loser);
                pair_count = pair_count + 1;
            }
        }
    }
    return;
}

// Sort pairs in decreasing order by strength of victory
void sort_pairs(void)
{
    // strongest victory to weakest
    //  puts win difference values into normal array WORKS MAYBE
    // printf("There are %i pairs\n", pair_count);
    int winamt[pair_count];
    for (int i = 0; i < pair_count; i++)
    {

        winamt[i] = (preferences[pairs[i].winner][pairs[i].loser] - preferences[pairs[i].loser][pairs[i].winner]);
        // printf("winamt is currently: %i\n", winamt[i]);
    }
    // sorts array
    int temp = 0;
    int count = 0;
    for (int j = pair_count - 1; j > 0; j--)
    {
        bool sorted = true;
        for (int k = pair_count - 1; k > count; k--)
        {
            if (winamt[k] > winamt[k - 1])
            {
                temp = winamt[k - 1];
                winamt[k - 1] = winamt[k];
                winamt[k] = temp;

                sorted = false;
            }
        }
        count = count + 1;
        if (sorted == true)
        {
            // printf("was sorted early\n");
            break;
        }
    }
    // printf("Sorted array is: ");
    for (int h = 0; h < pair_count; h++)
    {
        // printf("%i",winamt[h]);
        break;
    }
    // printf("\n");
    // puts back into pairs
    for (int m = 0; m < pair_count; m++)
    {
        for (int n = m; n < pair_count; n++)
        {
            if (winamt[m] == preferences[pairs[n].winner][pairs[n].loser] - preferences[pairs[n].loser][pairs[n].winner])
            {
                temp = pairs[m].winner;
                pairs[m].winner = pairs[n].winner;
                pairs[n].winner = temp;
                temp = pairs[m].loser;
                pairs[m].loser = pairs[n].loser;
                pairs[n].loser = temp;
            }
        }
    }

    return;
}

// is last pair true (locked), if so is me the winner
bool can_lock(int original_winner, int loser, int winner, int recursion_index, int original_loser)
{
    int new_winner = 0;
    int new_loser = 0;
    int counter = 0;
    if (original_winner == loser)
    {
        return false;
    }
    for (int i = recursion_index; i < candidate_count; i++)
    {
        // i goes through colums

        if (locked[loser][i] == true)
        {
            new_winner = loser; // who just won
            new_loser = i;      // who just lost

            if (!can_lock(original_winner, new_loser, new_winner, counter, original_loser))
            {
                // if rodrick loses but never wins, travel back to alice to see if she beats anyone else who also wins.
                return false;
            }
        }
    }
    // if loser ever wins // then check next loser if they win
    // rodrick does not win
    return true;
}
// Lock pairs into the candidate graph in order, without creating cycles
void lock_pairs(void)
{
    // goes thorugh all pairs
    for (int pair_index = 0; pair_index < pair_count; pair_index++)
    {
        if (can_lock(pairs[pair_index].winner, pairs[pair_index].loser, pairs[pair_index].winner, 0, pairs[pair_index].loser))
        {
            locked[pairs[pair_index].winner][pairs[pair_index].loser] = true;
        }
    }

    // debug stuff
    for (int j = 0; j < candidate_count; j++)
    {
        printf("%i ", j);
        for (int k = 0; k < candidate_count; k++)
        {
            printf("%i", locked[j][k]);
        }
        printf("\n ");
    }
}
// Print the winner of the election
void print_winner(void)
{
    bool check = false;
    for (int i = 0; i < candidate_count; i++)
    {
        check = false;
        for (int j = 0; j < candidate_count; j++)
        {
            if (locked[j][i] == true)
            {
                check = true;
            }
        }
        if (check == false)
        {
            printf("%s\n", candidates[i]);
            return;
        }
    }
}