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I wish I could be more specific with my question, but the problem is as the title suggests, check50's results do not seem to comport to mine. When I put it through check50, it fails on print_winner identifies Alice as winner of election and print_winner identifies Bob as winner of election although it does work for print_winner identifies Charlie as winner of election. However I have manually tested my code on the practice examples given on the walkthrough page and it seems to work with Alice and Bob, so I don't understand why my results are differing from check50's.

Here is my code (NB I am aware that I have not implemented the "Tie" part of the vote function yet.):

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

// 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;
    }

    int 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
        if (!vote(name))
        {
            printf("Invalid vote.\n");
        }
    }

    // Display winner of election
    print_winner();
}

// Update vote totals given a new vote
bool vote(string name)
{
    for(int i = 0; i < candidate_count; i++)
    {
        if (strcmp(name, candidates[i].name) == 0)
        {
            candidates[i].votes = candidates[i].votes + 1;
            return true;
        }
    }
    return false;
}

// Print the winner (or winners) of the election
void print_winner(void)
{
    int winner_int = candidates[0].votes;
    string winner;
    
     for (int i = 0; i < sizeof(candidates) / sizeof(candidates[0]); i++)
    {
        if (winner_int < candidates[i].votes)
        {
            winner = candidates[i].name;
        }
    }
    printf("%s\n", winner);
    return;
}
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So, I see a logic error in this bit of code:

if (winner_int < candidates[i].votes)
{
    winner = candidates[i].name;
}

Since you set winner_int equal to the number of votes that candidate[0] and never change that value, this will not always provide a valid winner in each situation. If candidate[0].votes == 3, candidate[1].votes == 4, and candidate[2].votes == 5 or candidate[2].votes <= 5, then this will work.

But, if candidate[0].votes == 3, candidate[1].votes == 5, and candidate[2].votes == 4, then it will incorrectly label candidate[2] as the winner because the last candidate will have more votes than winner_int is set to. You need to find a way to keep track of the current winning candidate's most votes to see if any other candidate gets more than that number, not a static value declared at the beginning.

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  • I haven't quite figured out how to fix it yet, but your diagnosis seems on the money. Many thanks. – BlueKhakis Feb 3 at 5:06

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