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Nov 15th, 2017
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__Sign Up__- package o1.election
- import scala.collection.mutable.Buffer
- /** The class `District` represents electoral districts (Finnish: ''vaalipiiri'').
- * Each district has a certain number of seats for which a (larger) number of
- * candidates compete in an election. Each district has its own candidates.
- *
- * A district object is immutable.
- *
- * @param name the name of the electoral district
- * @param seats the number of seats (elected positions) available
- * @param candidates the candidates vying for the seats in the district; there is always at least one candidate per district */
- class District(val name: String, val seats: Int, val candidates: Vector[Candidate]) {
- /** Returns a textual description of the district. The description is of the
- * form `Name: X candidates, Y seats`, where `Name` is the name of the district,
- * and `X` and `Y` the numbers of candidates and seats, respectively.
- * For instance, might return the string `Helsinki: 1064 candidates, 85 seats` */
- override def toString = this.name + ": " + this.candidates.size + " candidates, " + this.seats + " seats"
- /** Prints (to the console) a description of each candidate in this district, each on
- * a line of its own. A candidate's description is obtained by calling its `toString` method.
- *
- * NOTE TO STUDENTS: It's not usually a good idea to create "print some of your data"
- * methods ("return some information" methods are better), but we're still making one
- * as an exercise here. More about this in later chapters. */
- def printCandidates() = {
- for (candidate <- this.candidates) {
- println(candidate)
- }
- }
- /** Returns all the candidates in this district that belong to the party named by the parameter. */
- def candidatesFrom(party: String) = {
- var fromParty = Buffer[Candidate]()
- for (candidate <- this.candidates) {
- if (candidate.party == party) {
- fromParty += candidate
- }
- }
- fromParty.toVector
- }
- /** Returns the top candidate (Finnish: ''ääniharava'') of the district. That is, returns the
- * candidate with the highest number of votes. If multiple candidates have the same number of
- * votes, this method chooses one of them arbitrarily. It is assumed that every district always
- * has at least one candidate. */
- def topCandidate = {
- var topSoFar = this.candidates.head
- for (candidate <- this.candidates.tail) {
- if (candidate > topSoFar) {
- topSoFar = candidate
- }
- }
- topSoFar
- }
- /** Returns the total number of votes received by all the candidates,
- * that is, the total number of votes cast in this district. */
- def totalVotes = this.countVotes(this.candidates)
- /** Returns the total number of votes received by members of the party named by the parameter. */
- def totalVotes(party: String) = this.countVotes(this.candidatesFrom(party))
- /** Returns the total number of votes received by the given candidates. */
- def countVotes(candidates: Vector[Candidate]) = {
- var voteCount = 0
- for (candidate <- candidates) {
- voteCount += candidate.votes
- }
- voteCount
- }
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns a mapping from parties to their candidates. That is, returns a `Map` whose keys
- * are the names of all the parties that have candidates in this district. For each key,
- * the value is a vector containing the candidates from that party in arbitrary order.
- *
- * @see [[rankingsWithinParties]] */
- def candidatesByParty = { this.candidates.groupBy(_.party)
- //Map[String, Vector[Candidate]]()
- }
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns a mapping from parties to their top candidates. That is, returns a `Map` whose
- * keys are the names of all the parties that have candidates in this district. For each
- * key, the value is the candidate from that party with the most votes.
- *
- * If multiple candidates from a single party received the same number of votes, this method
- * chooses one of them arbitrarily. */
- def topCandidatesByParty = { candidatesByParty.mapValues(_.maxBy(_.votes))
- }
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns a mapping from parties to their vote totals. That is, returns a `Map` whose keys
- * are the names of all the parties that have candidates in this district. For each key, the
- * value is the number of votes received in total by all the members of that party in this district. */
- def votesByParty:Map[String, Int] = { candidatesByParty.mapValues(candidate(_.votes))
- //Map[String, Int]()
- }
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns a mapping from parties to ranking lists of those parties' candidates. That is,
- * returns a `Map` whose keys are the names of all the parties that have candidates in this
- * district. For each key, the value is a vector containing the candidates from that party
- * ''in order by the number of votes they received, starting with the highest''.
- *
- * If multiple candidates from a single party received the same number of votes, this method
- * orders them in an arbitrary way. */
- def rankingsWithinParties = Map[String, Vector[Candidate]]() // this is a non-working dummy implementation; this method will be implemented later
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns a vector containing the names of all the parties that have candidates in this
- * district, ordered by the total number of votes received by each party. Descending order
- * is used, so the party with the most votes comes first.
- *
- * If multiple parties received the same number of votes, this method orders them in an arbitrary way. */
- def rankingOfParties = { ???
- //Vector[String]() = { ???
- }
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns a mapping of candidates to their distribution figures (Finnish: ''vertailuluku'').
- * That is, returns a `Map` whose keys are all the candidates in this district and whose
- * values are the distribution figures of those candidates.
- *
- * The distribution figure of a candidate is obtained as follows. Take the position (rank) of
- * the candidate in the ranking list within his or her own party (as defined by
- * `rankingsWithinParties`). For instance, the most-voted-for candidate within a party has a
- * rank of 1, the second-most-voted-for has a rank of two, and so on. Divide the total number
- * of votes received by the candidate's party by the candidate's rank, and you have the
- * candidate's distribution figure.
- *
- * If multiple candidates from a single party received the same number of votes, the arbitrary
- * order chosen by `rankingsWithinParties` is used here, despite the fact that this is likely
- * to be a undesirable feature in a real-world system.
- *
- * @see [[votesByParty]]
- * @see [[rankingsWithinParties]]
- * @see [[electedCandidates]] */
- def distributionFigures = Map[Candidate, Double]() // this is a non-working dummy implementation; this method will be implemented later
- /** '''NOTE TO STUDENTS: THIS METHOD IS ONLY INTENDED FOR IMPLEMENTATION IN CHAPTER 9.4!'''
- *
- * Returns all the candidates who will be elected on the basis of the vote. The seats available
- * are given to the candidates with the highest distribution figures.
- *
- * If multiple candidates happen to have the same distribution figure, an arbitrary order is used,
- * despite the fact that this is likely to be a undesirable feature in a real-world system.
- *
- * @return the elected candidates in descending order by distribution figure
- * @see [[distributionFigures]] */
- def electedCandidates = Vector[Candidate]() // this is a non-working dummy implementation; this method will be implemented later
- }

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