1  package hlt;
 2  
 3  import java.util.ArrayList;
 4  import java.util.Iterator;
 5  
 6  public class Spiral implements Iterator<Position> {
 7  
 8      private Iterator<Position> iterator;
 9  
10      /**
11       * Creates a counter-clockwise spiral iterator of positions in a grid of dimension:
12       * dimension x dimension centered at origin
13       */
14      public Spiral(GameMap gameMap, Position origin, int dimension){
15          ArrayList<Position> positions = new ArrayList<>();
16          Position currentPosition = origin;
17          positions.add(currentPosition);
18          int sign = 1;
19          for (int i = 1; i <= dimension; i++){
20              for (int xStep = 1; xStep <= i; xStep++){
21                  currentPosition = currentPosition.offset(sign, 0);
22                  currentPosition = gameMap.normalize(currentPosition);
23                  positions.add(currentPosition);
24              }
25              for (int yStep = 1; yStep <= i; yStep++){
26                  currentPosition = currentPosition.offset(0, sign);
27                  currentPosition = gameMap.normalize(currentPosition);
28                  positions.add(currentPosition);
29              }
30              sign *= -1;
31          }
32          iterator = positions.subList(0, dimension * dimension).iterator();
33      }
34  
35      @Override
36      public boolean hasNext() {
37          return iterator.hasNext();
38      }
39  
40      //TODO: compute next position each call to next() rather than pre-computing the entire iterator
41      @Override
42      public Position next() {
43          return iterator.next();
44      }
45  }