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OK. I throw the towel. For the last 4 hours I have been getting the following errors in check50:

:( print_winner prints name when someone has a majority print_winner did not print winner of election

:( print_winner returns true when someone has a majority print_winner did not print winner and then return true

I have tested my code several times through debug50 and I can't find anything wrong, but check50 still show those errors.

The code is the following:

#include <cs50.h>
#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];

// Candidates have name, vote count, eliminated status
typedef struct
{
    string name;
    int votes;
    bool eliminated;
}
candidate;

// Array of candidates
candidate candidates[MAX_CANDIDATES];

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

// Function prototypes
bool vote(int voter, int rank, string 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, string argv[])
{
    // 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;
    }

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

    vc = (voter_count / 2) + 1;

    // Keep querying for votes
    for (int i = 0; i < voter_count; i++)
    {

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

            // 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;
        }

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

// Tabulate votes for non-eliminated candidates
void tabulate(void)
{
    int can = 0;

    for (int i = 0; i < voter_count; i++)
    {
        for (int j = 0; j < candidate_count; j++)
        {
            can = preferences[i][j];

            if (!candidates[can].eliminated)
            {
                candidates[can].votes++;
                break;
            }
        }
    }
    return;
}

// Print the winner of the election, if there is one
bool print_winner(void)
{
    string winner = " ";
    for(int i = 0; i < candidate_count; i++)
    {
        if(candidates[i].votes >= vc)
        {
            winner = candidates[i].name;
        }
    }

    if(strcmp(winner , " ") == 1)
    {
        printf("%s\n", winner);
        return true;
    }
    return false;
}

// Return the minimum number of votes any remaining candidate has
int find_min(void)
{
    int min = voter_count;

    for(int i = 0; i < candidate_count; i++)
    {
        if(candidates[i].votes < min && !candidates[i].eliminated)
        {
            min = candidates[i].votes;
        }
    }
    return min;
}

// 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].votes > min)
        {
            return false;
        }
    }
    return true;
}

// Eliminate the candidate (or candidates) 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;
}

Can you tell me where is the error that doesn't allow my code to pass check50?

Thank you very much.

Regards

1 Answer 1

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At least one problem is vc. From the spec (emphasis added):

Complete the implementation of runoff.c in such a way that it simulates a runoff election. You should complete the implementations of the vote, tabulate, print_winner, find_min, is_tie, and eliminate functions, and you should not modify anything else in runoff.c (and the inclusion of additional header files, if you’d like).

3
  • Thanks for pointing this out. I will remove the associated code and try it.
    – pampero43
    Commented Apr 30, 2022 at 20:35
  • I removed the variable vc and implemented a different way of checking the votes inside the code I had to write. Unfortunately, it didn't work. I still get the errors described in my question. Thanks DinoCoderSaurus.
    – pampero43
    Commented Apr 30, 2022 at 20:44
  • OK. I found the error. In line if(strcmp(winner , " ") == 1), instead of == 1 should say != 0.
    – pampero43
    Commented May 2, 2022 at 19:31

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