diff options
Diffstat (limited to 'src/ch/epfl')
-rw-r--r-- | src/ch/epfl/xblast/Lists.java | 43 |
1 files changed, 24 insertions, 19 deletions
diff --git a/src/ch/epfl/xblast/Lists.java b/src/ch/epfl/xblast/Lists.java index f468788..51e76b0 100644 --- a/src/ch/epfl/xblast/Lists.java +++ b/src/ch/epfl/xblast/Lists.java | |||
@@ -3,6 +3,8 @@ package ch.epfl.xblast; | |||
3 | import java.util.ArrayList; | 3 | import java.util.ArrayList; |
4 | import java.util.Collections; | 4 | import java.util.Collections; |
5 | import java.util.List; | 5 | import java.util.List; |
6 | import java.util.stream.Collectors; | ||
7 | import java.util.stream.Stream; | ||
6 | 8 | ||
7 | /** | 9 | /** |
8 | * Lists utility class providing common operations on lists. | 10 | * Lists utility class providing common operations on lists. |
@@ -13,30 +15,33 @@ import java.util.List; | |||
13 | public final class Lists { | 15 | public final class Lists { |
14 | 16 | ||
15 | /** | 17 | /** |
16 | * Return a symmetric version of the list. | 18 | * Returns a reversed copy of the given list, leaving the original one unmodified. |
17 | * | 19 | * |
18 | * @param l the input list | 20 | * @param l the list to reverse |
19 | * @return mirroredList the mirrored list | 21 | * @param <T> the type of the list's elements |
22 | * @return a reversed copy of the list. | ||
23 | */ | ||
24 | public static <T> List<T> reversed(List<T> l) { | ||
25 | List<T> r = new ArrayList<>(l); | ||
26 | Collections.reverse(r); | ||
27 | return r; | ||
28 | } | ||
29 | |||
30 | /** | ||
31 | * Returns a symmetric version of the list, without repeating the last element of the input list. | ||
32 | * For instance, mirrored([kay]) will return [kayak]. | ||
33 | * | ||
34 | * @param l the input list | ||
35 | * @param <T> the type of the list's elements | ||
36 | * @return the mirrored list | ||
20 | * @throws IllegalArgumentException if the given list is empty | 37 | * @throws IllegalArgumentException if the given list is empty |
21 | */ | 38 | */ |
22 | public static <T> List<T> mirrored(List<T> l) { | 39 | public static <T> List<T> mirrored(List<T> l) { |
23 | if (l.size() == 0) { | 40 | if (l == null || l.size() == 0) throw new IllegalArgumentException(); |
24 | throw new IllegalArgumentException(); | ||
25 | } | ||
26 | |||
27 | List<T> mirroredList = new ArrayList<T>(); | ||
28 | List<T> rightSide = new ArrayList<T>(); | ||
29 | |||
30 | for (int i = 0; i < l.size() - 1; i++) { | ||
31 | rightSide.add(l.get(i)); | ||
32 | } | ||
33 | |||
34 | Collections.reverse(rightSide); | ||
35 | |||
36 | mirroredList.addAll(l); | ||
37 | mirroredList.addAll(rightSide); | ||
38 | 41 | ||
39 | return mirroredList; | 42 | return Stream |
43 | .concat(l.stream(), Lists.reversed(l).stream().skip(1)) | ||
44 | .collect(Collectors.toList()); | ||
40 | } | 45 | } |
41 | 46 | ||
42 | } | 47 | } |