PSet3 Plurality - Segmentation Fault when exiting main

Question

My code seems to function properly until I try to exit main. At this point it reports a segmentation fault. This only occurs when there is a tie.

Here is my code:

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

// Max number of candidates
#define MAX 9

// Candidates have name and vote count
typedef struct
{
    string name;
    int votes;
}
candidate;

// Array of candidates
candidate candidates[MAX];

// Number of candidates
int candidate_count;
int voter_count;

// Other global variables
int v;


// Function prototypes
bool vote(string name);
void print_winner(void);



int main(int argc, string argv[])
{
    // Check for invalid usage
    if (argc < 2)
    {
        printf("Usage: plurality [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].name = argv[i + 1];
        candidates[i].votes = 0;
    }

    voter_count = get_int("Number of voters: ");

    // Loop over all voters
    for (int i = 0; i < voter_count; i++)
    {
        string name = get_string("Vote: ");

        // Check for invalid vote and update vote count

        if (!vote(name))
        {
            printf("Invalid vote.\n");
        }
        else if (vote(name))
        {
            candidates[v].votes = candidates[v].votes + 1;
        }
    }

    // Display winner of election
    print_winner();

    // with or without this 'return 0;' there is a segmentation fault
    return 0;
}

// Update vote totals given a new vote
bool vote(string name)
{
    // checks if the vote is valid
    for (v = 0; v < candidate_count; v++)
    {
        if (strcmp(name, candidates[v].name) == 0)
        {
            return true;
        }
    }

    return false;
}

// Print the winner (or winners) of the election
void print_winner(void)
{
    int top[] = {};
    int num = 0;
    int big = 0;

    //finds the largest number
    for (int i = 0; i < candidate_count; i++)
    {
        if (candidates[i].votes > big)
        {
            big = candidates[i].votes;
        }
    }

    // checks if there are multiple winners, populates a new array with the locations of the winners, and counts the number of winners.
    for (int i = 0; i < candidate_count; i++)
    {
        if (candidates[i].votes == big)
        {
            top[num] = i;
            num += 1;
        }
    }

    // prints the winner(s) names
    for (int i = 0; i < num; i++)
    {
        printf("%s\n", candidates[top[i]].name);
    }

    return;
}

I am also getting these errors when I run check50:

:( vote produces correct counts when all votes are zero
    vote function did not correctly update vote totals
:( vote produces correct counts after some have already voted
    vote function did not correctly update vote totals

Does anyone know what the problem is?

Answer 1

I found a solution.

I replaced:

    for (int i = 0; i < candidate_count; i++)
    {
        if (candidates[i].votes == big)
        {
            top[num] = i;
            num += 1;
        }
    }

with

        if (candidates[i].votes == big && num < candidate_count)
        {
            top[num] = i;
            num = num + 1;
        }

It no longer reports a segmentation fault when there is a tie.