# Gale-Shapleyの実装で多次元配列の問題

すべてが問題なく、私は解決策に近いと思う。しかし、嗜好データ（マルチディジット配列）にアクセスすると、何か奇妙なことが起きています。 2番目のインデックス` kTaxiIndex `は正しい値を持ちますが、インデックスを作成するときに同じ行の別の列からデータを取得しています。私はすでに変数を動かしています。誰もがここで何が起こっている少しわずかな手がかりを持っていますか？

どんな助けも大歓迎です。

``````class TaxiScheduler {

ArrayList acceptorTaxis;
ArrayList proposorPassengers;
Integer [] waitingList; //index represent taxis, contents passengers
ArrayList rejectionPool;   //where unmatched passengers are kept
Integer [] rejectionCounter;    //determines the KBest option for that passenger
Double [][] distancePreferences;      //unique preference structure

public TaxiScheduler(){

}

public Integer[] doGaleShapley(ArrayList taxis, ArrayList passengers){

acceptorTaxis = taxis;
proposorPassengers = passengers;
waitingList = new Integer [acceptorTaxis.size()];   //keeps best current match
rejectionPool = new ArrayList();   //rejected passengers' indexes
rejectionCounter = new Integer [proposorPassengers.size()];  //keeps track of rejections per passenger
distancePreferences = new Double[proposorPassengers.size()][acceptorTaxis.size()];

initPoolandCounter();   //No passenger has been rejected, but all are included in the rejecion (not matched) pool
calculatePreferences();//distances between taxis and passengers

/*
* Every rejected passenger turns to its next (1st, 2nd, 3rd,...) closest taxi
* Every taxi with more than one proposal keeps the closest passenger in the waitingList and
* rejects other proposing passengers
*/
ListIterator itrRejected = this.rejectionPool.listIterator();
while(!this.rejectionPool.isEmpty())
{
if(!itrRejected.hasNext())  //end of list
itrRejected = this.rejectionPool.listIterator();

int newPassengerIndex = (Integer) itrRejected.next().intValue();
int kTaxiIndex = getKBestOption(this.rejectionCounter[newPassengerIndex], newPassengerIndex); //Get K-best based on number of rejections

itrRejected.remove();   //remove current passenger from rejected list

if(waitingList[kTaxiIndex]== null ){ //taxi is vacant!
waitingList[kTaxiIndex] = newPassengerIndex;   //match w/ closest taxi
}else{ //compare, keep the best and pool rejected, update rejection counter
int currentPassengerIndex = waitingList[kTaxiIndex].intValue();

Double d1 = distancePreferences[currentPassengerIndex][kTaxiIndex];
Double d2 = distancePreferences[newPassengerIndex][kTaxiIndex];

if(d1.compareTo(d2) > 0){    //new passenger is closer i.e. d1 > d2
waitingList[kTaxiIndex] = new Integer(newPassengerIndex);   //set new passenger as new match

}else{  //current passenger is preferred
}
}
}
Logger.getLogger("data").log(Level.INFO, "rejectedList = "+printPool(), "");
return waitingList;
}

private void initPoolandCounter() {
rejectionCounter = new Integer[this.proposorPassengers.size()];

for(int i = 0;i< rejectionCounter.length;i++)
{
rejectionCounter[i]=0;
}
}

//Works with indexes, look up on preference structure
private Double getDistance(Integer passengerIndex, Integer taxiIndex) {
return distancePreferences[passengerIndex.intValue()][taxiIndex.intValue()];
}

/**
*Fills the preferences structure with distances between taxis and passengers
*
*/

private void calculatePreferences() {
double distance = -1;
StringBuffer buff = new StringBuffer();

try {
for (int iPass = 0; iPass < this.proposorPassengers.size(); iPass++){
PassengerMovement passMov = (PassengerMovement) this.proposorPassengers.get(iPass);
GeoPointExt passGeo = new GeoPointExt(passMov.getLatitude(),passMov.getLongitude());
buff.append(iPass+":\t");
for (int iTaxi = 0; iTaxi < this.acceptorTaxis.size(); iTaxi++){
TaxiMovement taxiMov = (TaxiMovement) this.acceptorTaxis.get(iTaxi);
GeoPointExt taxiGeo = new GeoPointExt(taxiMov.getLatitude(), taxiMov.getLongitude());

distance = Haversine.getDistance(taxiGeo, passGeo, DistanceUnit.Kilometers);
this.distancePreferences[iPass][iTaxi] = new Double(distance);
//TODO: Inverted distances!!!
buff.append(distancePreferences[iPass][iTaxi].toString().substring(0, 5) +"\t");

//Logger.getLogger(TaxiScheduler.class.getName()).log(Level.SEVERE, "PREFS = ["+passMov.getPassengerMovementPK().getMobileNo()+"]["+taxiMov.getTaxiMovementPK().getPlateNo()+"]");
//Logger.getLogger(TaxiScheduler.class.getName()).log(Level.SEVERE, "PREFS = ["+iPass+"]["+iTaxi+"]("+this.distancePreferences[iPass][iTaxi].toString().substring(0, 4));
}
buff.append("\n");
}
}catch(NullPointerException ex)
{
Logger.getLogger(TaxiScheduler.class.getName()).log(Level.SEVERE, "distance = "+distance, ex);
}

Logger.getLogger(TaxiScheduler.class.getName()).log(Level.SEVERE, "TOTAL PREF = \n"+buff.toString());

}

/*
* Returns index of the taxi that is k-best option for that passenger
*
* @param k The k-best (closest) taxi to be retrieved, 0 being the closest
* @param passIndex The passenger index
* @return  K-closest taxi index for this passenger
*/
private int getKBestOption(int k, int passIndex){
Double [] passPreferences = this.distancePreferences[passIndex];    //Preferences for the taxi in that index
List pPreferences = Arrays.asList(passPreferences);
ArrayList originalOrder = new ArrayList(pPreferences);

Collections.sort(pPreferences); //sort taxi distances
Double kDistance = (Double) pPreferences.get(k); //get k-smallest distance
int ind = originalOrder.indexOf(kDistance);  //find index of this value in the original array, even if repeated still KBest
return ind;
}

private String printPool() {
StringBuffer buff = new StringBuffer();
int c = 0;

for(Integer x:this.rejectionPool)
{
buff.append(x+"["+rejectionCounter[x]+"]  ");
c++;
}
return buff.toString();
}

/*
* Add this element to rejection pool and updates its rejection counter
*
* @param passengerToPool Passenger index to add to the pool
* @param itrRejected iterator used in the rejectionPool
*/
private void addToPool(int passengerToPool, ListIterator itrRejected) {
//check whether this passenger is already in the pool
int rIndex = rejectionPool.indexOf(passengerToPool);

if(rIndex == -1){ //not in the pool
this.rejectionCounter[passengerToPool]+=1;
if(this.rejectionCounter[passengerToPool] < this.acceptorTaxis.size())  //if has not been rejected by all taxis

}else{  //was already pooled, leave it there and increase counter
this.rejectionCounter[rIndex]+=1;
}
}
}
``````
0

@DaveNewton何が起こっているのですか？distancePreferences多次元配列のインデックスを作成するときに、インデックスが正常であっても、別のセルのコンテンツを取得しています。本当に奇妙なのは、列インデックスのみが間違っていることです。つまり、同じ行（別の列）の位置を取得しています。

## 1 答え

あなたのバグを見つけるのを助けるために私が提案できるもの：

• You have a lot of collections, in particular arrays of differing sizes. It doesn't really surprise me that you're getting some "out of whack" positions given this
• It looks like you've taken an algorithm expressed in a non-OO language (or perhaps pseudocode) - it could be worth setting up a new class to represent a `Taxi` and a `Passenger`, holding all the pertinent details inside, rather than trying to index into a particular array position of a particular array
• You have a mixture of method parameters and member variables that means your `TaxiScheduler` can actually only deal with one call to `doGaleShapley()` at a time. This will probably bite you later on unless you move all those member variables into the method
• Using "naked" `ArrayList`s is a double-no-no: `List` gives you type-safety while not forcing your client to use an `ArrayList`
• Refactor your `doGaleShapley()` method into smaller, self-contained, well-named methods that do one thing only
• Use Unit Tests to simulate each possible situation. Each test should be named after a desired functionality (e.g. `shouldReturnEmptyWaitingListIfNoPassengersProvided`) and consist of `Given - When - Then` statements that set up a scenario, exercise your function, and verify the results are as expected. If you've refactored your big method into smaller ones, it will be very easy to name your tests and make sure you're covering everything. You can also use a code coverage tool like Cobertura to ensure all your branches are being hit.
• If, after doing all this, you still can't figure it out, you should at least have a smaller snippet of code that you can post here :-)
0

doGaleShapleyのリファクタリングについて、何かを時間をとってお勧めしますか？私にとってはとてもシンプルなようです。このコードは意図せずにここの擬似コードen.wikipedia.org/wiki/Gale-Shapley_algorithmと似ています。