tideman.c

#include <ctype.h>
#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <math.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;
int candidate_count;
// Function prototypes
bool cycle(int start , int end);
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[])
{
    // TODO
    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[])
{
    // TODO
    for(int i=0 ; i<candidate_count ; i++)
    {
        for(int j=i + 1; j<candidate_count ; j++)
        {
            preferences[ranks[i]][ranks[j]]++;
        }
    }
    return;
}
// Record pairs of candidates where one is preferred over the other
void add_pairs(void)
{
    // TODO
    for(int i=0 ; i<candidate_count ; i++)
    {
        for(int j=i + 1; j<candidate_count ; j++)
        {
            if(preferences[i][j] > preferences[j][i])
            {
                pairs[pair_count].winner = i;
                pairs[pair_count].loser = j;
                pair_count++;
            }
            else if(preferences[i][j] < preferences[j][i])
            {
                pairs[pair_count].winner = j;
                pairs[pair_count].loser = i;
                pair_count++;
            }
        }
    }
    return;
}
// Sort pairs in decreasing order by strength of victory
void sort_pairs(void)
{
    // TODO
    pair temp;
    for(int i=0 ; i<pair_count ; i++)
    {
        for(int j=i + 1; j<pair_count ; j++)
        {
            if(pairs[i].winner - pairs[i].loser > pairs[j].winner - pairs[j].loser )
            {
                temp = pairs[j];
                pairs[j] = pairs[i];
                pairs[i] = temp;
            }
        }
    }
    return;
}
// Lock pairs into the candidate graph in order, without creating cycles
void lock_pairs(void)
{
    // Loop through pairs
    for (int i = 0; i < pair_count; i++)
    {
        // If cycle function returns false, lock the pair
        if (!cycle(pairs[i].winner , pairs[i].loser))
        {
            locked[pairs[i].winner][pairs[i].loser] = true;
        }
    }
    return;
}
// Print the winner of the election
void print_winner(void)
{
    // TODO
    int isfalse = 0;

    for(int i=0 ; i<candidate_count ; i++)
    {

        int isfalse = 0;
        for(int j = 0; j<candidate_count ; j++)
        {
            if(locked[j][i]==false)
            {
                isfalse++;
                if(isfalse == candidate_count)
                {
                    printf("%s\n",candidates[i]);
                }
            }
        }
        
    }
    
    
    return;
}
bool cycle(int start , int end)
{
    if(start == end)
    {
        return true;
    }
    for(int i=0 ; i<candidate_count ; i++)
    {
        if(locked[end][i])
        {
            if(cycle(start , i))
            {
                return true;
            }
        }
    }
    return false;
}