Could use some help with Runoff. If I do a simple clear winner (all voters vote for the same person as first choice) it prints out the winner just fine. But if I do the test input that the problem set provides, it prints out all 3 candidates names. Help would be appreciated with whatever function(s) I messed up.
#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;
// 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;
}
// 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)
{
//look for candidate called name
//if found, update preferences so that they are the (voter)'s (rank) preference and return true
for (int i = 0; i < candidate_count; i++)
{
if (strcmp(candidates[i].name, name) == 0) //if match for name found
{
preferences[voter][rank] = i;
return true;
}
}
//if not found, return false
return false;
}
// Tabulate votes for non-eliminated candidates
void tabulate(void)
{
//update vote counts for all non-eliminated candidates
for (int j = 0; j < 1; j++)
{
//incrementing through total number of voters
for (int i = 0; i < voter_count; i++)
{
int n = preferences[i][j];
if (candidates[n].eliminated == false)
{
candidates[n].votes++;
j=0;
}
else
//if candidate is eliminated, go to voter's nextp preference
{
i--;
j++;
}
}
}
//remember each voter votes for their highest preference candidate who has not yet been eliminated
return;
}
// Print the winner of the election, if there is one
bool print_winner(void)
{
//if any candidate has more than half the vote, print their name and return true
int votesneeded = voter_count / 2 + 0.5;
bool winner;
for (int i = 0; i < candidate_count; i++)
{
if (candidates[i].votes > votesneeded)
{
winner = true;
printf("%s\n", candidates[i].name);
return winner;
}
}
//if no one has won, print nothing and return false
return false;
}
// Return the minimum number of votes any remaining candidate has
int find_min(void)
{
//initialize a, will use this as the min vote count. start it as the total number of voters
int a = voter_count;
//return minimum number of votes of anyone still in the election (eliminated = false)
//iterate through each candidate
for (int i = 0; i < candidate_count; i++)
{
//if eliminated = false,
if (candidates[i].eliminated == false && a > candidates[i].votes)
a = candidates[i].votes;
}
return a;
}
// Return true if the election is tied between all candidates, false otherwise
bool is_tie(int min)
{
//input is minimum number of votes, int min
for (int i = 0; i < candidate_count; i++)
{
//returns true if the election is tied between all remaining candidates
if (candidates[i].eliminated == false && candidates[i].votes == min)
return true;
}
//otherwise return false
return false;
}
// 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, which is what we calculated in find_min
for (int i = 0; i < candidate_count; i++)
// if candidate's votes are equal to or less than minimum votes, change .eliminated to true
if (!candidates[i].eliminated)
{
if (candidates[i].votes == min)
{
candidates[i].eliminated = true;
}
}
return;
}
