/// <summary>
/// Gets the winning vote.
/// Excludes any already chosen votes from the process.
/// </summary>
/// <param name="voterRankings">The voter rankings.</param>
/// <param name="chosenChoices">The already chosen choices.</param>
/// <returns>Returns the winning vote.</returns>
/// <exception cref="System.ArgumentNullException">
/// </exception>
private RankResult GetWinningVote(IEnumerable <VoterRankings> voterRankings, RankResults chosenChoices)
{
if (voterRankings == null)
{
throw new ArgumentNullException(nameof(voterRankings));
}
if (chosenChoices == null)
{
throw new ArgumentNullException(nameof(chosenChoices));
}
// Initial conversion from enumerable to list
List <VoterRankings> localRankings = RemoveChoicesFromVotes(voterRankings, chosenChoices.Select(c => c.Option));
int voterCount = localRankings.Count();
int winCount = voterCount / 2 + 1;
string eliminated = "";
bool eliminateOne = false;
while (true)
{
var preferredVotes = GetPreferredCounts(localRankings);
if (!preferredVotes.Any())
{
break;
}
ChoiceCount best = preferredVotes.MaxObject(a => a.Count);
if (best.Count >= winCount)
{
return(new RankResult(best.Choice, $"Baldwin Eliminations: [{eliminated}]"));
}
// If no more choice removals will bump up lower prefs to higher prefs, return the best of what's left.
if (!localRankings.Any(r => r.RankedVotes.Count() > 1))
{
return(new RankResult(best.Choice, $"Baldwin Eliminations: [{eliminated}]"));
}
string leastPreferredChoice = GetLeastPreferredChoice(localRankings);
eliminated += Comma(eliminateOne) + leastPreferredChoice;
RemoveChoiceFromVotes(localRankings, leastPreferredChoice);
eliminateOne = true;
}
return(null);
}
/// <summary>
/// Gets the winning vote, instant runoff style.
/// </summary>
/// <param name="voterRankings">The voters' rankings.</param>
/// <param name="chosenChoices">The already chosen choices that we should exclude.</param>
/// <returns>Returns the winning vote, if any. Otherwise, null.</returns>
/// <exception cref="System.ArgumentNullException">
/// </exception>
private RankResult GetWinningVote(IEnumerable <VoterRankings> voterRankings, RankResults chosenChoices)
{
if (voterRankings == null)
{
throw new ArgumentNullException(nameof(voterRankings));
}
if (chosenChoices == null)
{
throw new ArgumentNullException(nameof(chosenChoices));
}
List <VoterRankings> localRankings = RemoveChoicesFromVotes(voterRankings, chosenChoices.Select(c => c.Option));
int voterCount = localRankings.Count(v => v.RankedVotes.Any());
int winCount = voterCount / 2 + 1;
string eliminated = "";
bool eliminateOne = false;
while (true)
{
var preferredVotes = GetPreferredCounts(localRankings);
if (!preferredVotes.Any())
{
break;
}
var best = preferredVotes.MaxObject(a => a.Count);
if (best.Count >= winCount)
{
return(new RankResult(best.Choice, $"IRV Eliminations: [{eliminated}]"));
}
var worst = preferredVotes.MinObject(a => a.Count);
eliminated += Comma(eliminateOne) + worst.Choice;
RemoveChoiceFromVotes(localRankings, worst.Choice);
eliminateOne = true;
}
return(null);
}