Algorithms(week3, problemset)

1. Plurality

#include <stdio.h>
#include <cs50.h>
#include <string.h>
 
#define MAX 9
 
typedef struct{
 
    char *name;
    int votes;
 
}candidate;
 
//array of candidates
candidate candidates[MAX];
 
//number of candidates
int candidate_count;
 
//functions
bool vote(char *name);
void print_winner();
 
int main(int argc, char *argv[]){
    //Plurality vote
        //every voter chooses one candidate
        //whichever candidate has the msot votes wins
 
    //./plurality Alice Bob Charlie
    //Number of voters : 4
    //Vote: Alice
    //Vote: Bob
    //Vote: Charlie
    //Vote: Charlie
    //Charlie
 
//2 functions
    //vote
        //look for a candidate called name.
        //if candidate found, update their vote total and return true.
        //if no candidate found, dont update any vote totals and return false
    //print_winner
        //print the name of the candidate(s) who have the most votes.
 
    //check for invalid usage
    if(argc < 2){
        printf("Usage: plurality [candidate ...]\n");
        return 1;
    }
 
    //populate array of candidates
    //check for error
    candidate_count = argc - 1;
    if(candidate_count > MAX){
        printf("Maxium number of candidates is %i\n", MAX);
        return 2;
    }
 
    for(int i = 0; i < candidate_count; i++){
        candidates[i].name = argv[i + 1];
        candidates[i].votes = 0;
    }
 
    //prints array
    /*for(int i = 0; i < candidate_counts; i++){
        printf("%i %s %i\n", i, candidates[i].name, candidates[i].votes);
    }*/
 
    //receive number of voters
    int voters = get_int("Number of voters: ");
 
    //iterate and check for invalid votes
    for(int i = 0; i < voters; i++){
        char *name = get_string("Vote: ");
        if(!vote(name)){
            printf("Invalid vote.\n");
        }
    }
 
    print_winner();
    return 0;
 
}
 
bool vote(char *name){
 
    for(int i = 0; i < candidate_count; i++){
        if(strcmp(name, candidates[i].name) == 0){
            candidates[i].votes += 1;
            return true;
        }
    }
    return false;
}
 
void print_winner(){
 
    //finds the highest votes
    int highest = 0;
    for(int i = 0; i < candidate_count; i++){
        if(candidates[i].votes > highest) highest = candidates[i].votes;
    }
 
    //prints highest voters
    for(int i = 0; i < candidate_count; i++){
        if(candidates[i].votes == highest) printf("%s\n", candidates[i].name);
    }
    return;
}

2. Runoff

#include <cs50.h>
#include <stdio.h>
#include <string.h>
 
#define MAX_VOTERS 100
#define MAX_CANDIDATES 9
 
int preferences[MAX_VOTERS][MAX_CANDIDATES];
 
typedef struct{
    char *name;
    int votes;
    bool eliminated;
}candidate;
 
candidate candidates[MAX_CANDIDATES];
 
int voter_count;
int candidate_count;
 
//Function prototypes
bool vote(int voter, int rank, char *name);
void tabulate();
bool print_winner();
int find_min();
bool is_tie(int min);
void eliminate(int min);
 
int main(int argc, char *argv[]){
    //Runoff Vote
        //Every voter ranks their preferences
        //if a candidate has a majority (more than half) of the ovtes,
        // they are the winner
        //otherwise, eliminate the candidate with the fewest votes
        //and re-run the election without them
 
    //Check for invalid usage
    if(argc < 2){
        printf("Usage: runoff [candidate...]\n");
        return 1;
    }
 
    //Populate array of candidates
    candidate_count = argc - 1;
    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++){
        candidates[i].name = argv[i + 1];
        candidates[i].votes = 0;
        candidates[i].eliminated = false;
    }
 
    //receive number of votes
    voter_count = get_int("Number of voters: ");
    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++){
            //record vote, unless it's invalid
            char *name = get_string("Rank %i: ", j + 1);
            if(!vote(i, j, name)){
                printf("Invalid vote\n");
            }
        }
        printf("\n");
    }
 
    // Keep holding runoffs untsil winner exists
    while(true){
        // Calculate votes given remaining candidates
        tabulate();
        // Check if election has been won
        if(print_winner()){
            break;
        }
 
        int min = find_min();
        if(is_tie(min)){
            for(int i = 0; i < candidate_count; i++){
                if(!candidates[i].eliminated){
                    printf("%s\n", candidates[i].name);
                }
            }
            break;
        }
        eliminate(min);
 
        // Eliminate last-place candidates
        // If tie, everyone wins
        // Eliminate anyone with minimum number of votes
        // 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){
 
    bool has_candidate = false;
    //Look for a candidate called name,
    //if candidate found, update preferences so that they are the voter's
    for(int i = 0; i < candidate_count; i++){
        if(strcmp(name, candidates[i].name) == 0) {
            preferences[voter][rank] = i;
            return true;
        }
    }
 
    //if no candidate found, dont update and return false
    return false;
}
 
// Tabulate votes for non-eliminated candidates
void tabulate(void)
{
    //update vote counts for all non-eliminated candidates
    for(int i = 0; i < voter_count; i++){
        //recall that each voter votes for their heighest preference
        for(int j = 0; j < candidate_count; j++){
            //candidate who has not yet been eliminated.
            //only update vote who are still in the race
            if(!candidates[preferences[i][j]].eliminated){
                candidates[preferences[i][j]].votes += 1;
                break;
            }
        }
    }
 
    // TODO
    return;
}
 
// Print the winner of the election, if there is one
bool print_winner(void)
{
    //if any candidate has more ethan half the vote, print out their
    //their name and return true
    for(int i = 0; i < candidate_count; i++){
        if(voter_count/2 < candidates[i].votes){
            printf("%s\n", candidates[i].name);
            return true;
        }
    }
 
    //if nobody has won the election yet, return false
    return false;
}
 
// Return the minimum number of votes any remaining candidate has
int find_min(void)
{
    //return the minimum number of votes of anyone still in the elction.
    //return candidates who has not been eliminated
    int min = MAX_VOTERS;
    for(int i = 0; i < candidate_count; i++){
        if(!candidates[i].eliminated && min > candidates[i].votes)
        min = candidates[i].votes;
    }
    // TODO
    return min;
}
 
// Return true if the election is tied between all candidates, false otherwise
bool is_tie(int min)
{
    //accepts the minimum number of votes min as input.
    for(int i = 0; i < candidate_count; i++){
        if(!candidates[i].eliminated && candidates[i].votes != min){
            return false;
        }
    }
    //returns true if the election is tied between all remaining candidates
    //, and return false otherwise.
    // TODO
    return true;
}
 
// Eliminate the candidate (or candidiates) in last place
void eliminate(int min)
{
    //eliminate anyone still in the race who has the min number of votes
    //if votes are the same, should eliminate two candidates
    for(int i = 0; i < candidate_count; i++){
        if(!candidates[i].eliminated && candidates[i].votes == min){
            candidates[i].eliminated = true;
        }
    }
    // TODO
    return;
}
 
 
 
 
 
 
 
 
 

3. Tideman

COULD NOT FINISH TIDEMAN WITH MY CURRENT UNDERSTANDING OF PROGRAMMING

Will get back to it in the future

#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;
int candidate_count;
 
// 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[])
{
    //- look for a candidate called name
    //- if candidate found, update ranks and return true. ranks[i] is the voter's ith preference.
    //- if no candidate found, dont update any ranks and return false.
    // TODO
 
    for(int i = 0; i < candidate_count; i++){
        if(strcmp(candidates[i], name) == 0){
            ranks[i] = rank;
            return true;
        }
    }
    return false;
}
 
// Update preferences given one voter's ranks
void record_preferences(int ranks[])
{
    //- update the preferences array based on the current voter's rank
    // TODO
 
    for(int i = 0; i < candidate_count; i++){
        for(int j = 0; j < candidate_count; j++){
            if(ranks[i] < ranks[j]) preferences[i][j] += 1;
        }
    }
 
    for(int i = 0; i < candidate_count; i++){
        for(int j = 0; j < candidate_count; j++){
            printf("%i\t", preferences[i][j]);
        }
        printf("\n");
    }
    return;
}
 
// Record pairs of candidates where one is preferred over the other
void add_pairs(void)
{
  //  - add each pair of candidates to pairs array if one candidate is preferred over the other.
//    - udpate global variable pair_count to be the total number of pairs
 
    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;
                pair_count += 1;
            }
            /*else if(preferences[i][j] < preferences[j][i]){
                pairs[pair_count].winner = i;
                pairs[pair_count].loser = j;
                pair_count += 1;
            }*/
 
        }
    }
 
    //before sort
    for(int i = 0; i < pair_count; i++){
        printf("pairs %ith is winner %i and loser %i\n", i, pairs[i].winner, pairs[i].loser);
    }
    printf("\n");
    // TODO
    return;
}
 
// Sort pairs in decreasing order by strength of victory
void sort_pairs(void)
{
    // TODO
    //bubble sort
    //backwards, placing the highest value first
    for(int i = 0; i < pair_count - 1; i++){
        int ifirstDiff = preferences[pairs[i].winner][pairs[i].loser];
        int isecondDiff = preferences[pairs[i].loser][pairs[i].winner];
        int iComp = ifirstDiff - isecondDiff;
 
        for(int j = i + 1; j < pair_count; j++){
            int jfirstDiff = preferences[pairs[j].winner][pairs[j].loser];
            int jsecondDiff = preferences[pairs[j].loser][pairs[j].winner];
            int jComp = jfirstDiff - jsecondDiff;
 
            if(iComp < jComp){
                pair temp = pairs[j];
                pairs[j] = pairs[i];
                pairs[i] = temp;
            }
        }
    }
 
    for(int i = 0; i < pair_count; i++){
        printf("pairs %ith is winner %i and loser %i\n", i, pairs[i].winner, pairs[i].loser);
    }
    return;
}
 
// Lock pairs into the candidate graph in order, without creating cycles
void lock_pairs(void)
{
    //- update locked to create the locked graph by adding all edges
    //in decreasing order of vicotry strength, as long as there is no cycle
    // TODO
    locked[pairs[0].winner][pairs[0].loser] = true;
    for(int i = 1; i < pair_count; i++){
        int a = pairs[i].winner;
        int b = pairs[i].loser;
        for(int j = i + 1; j < pair_count; j++){
            int z = pairs[j].winner;
 
            if(a > z) locked[a][b] = true;
            else break;
        }
 
    }
 
    for(int i = 0; i < candidate_count; i++){
        for(int j = 0; j < candidate_count; j++){
            printf("%s\t", locked[i][j] ? "true" : "false");
        }
        printf("\n");
    }
 
    return;
}
 
// Print the winner of the election
void print_winner(void)
{
    //-print out the winner of the election, who will be the source of the graph
    //- you may assume there may be no more than one source.
    int count = 0;
    int winner = 0;
    for(int i = 0; i < pair_count; i++){
        int temp = 0;
        for(int j = 0; j < pair_count; j++){
            if(locked[i][j]) {
                temp ++;
                if(count < temp){
                    count = temp;
                    winner = i;
                } else if (count == temp){
                    winner = i;
                }
            }
        }
    }
 
    printf("%s\n", candidates[winner]);
    // TODO
    return;
}
 
/*bool lockrecursive(int winner, int loser){
 
    bool check = true;
    if(winner < 0){
        winner = 0;
        return true;
    }
    if(loser < 0){
        loser = 0;
        return true;
    }
 
    for(int i = 0; i < winner; i++){
        if(locked[winner][i]) check = false;
    }
}*/