Add lists and maps functions

1 files changed, 48 insertions, 0 deletions

diff --git a/src/ch/epfl/xblast/Lists.java b/src/ch/epfl/xblast/Lists.java
index cc6a1c8..bf0cafa 100644
--- a/src/ch/epfl/xblast/Lists.java
+++ b/src/ch/epfl/xblast/Lists.java
@@ -2,6 +2,7 @@ package ch.epfl.xblast;
 
 import java.util.*;
 import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
 /**
@@ -181,4 +182,51 @@ public final class Lists {
                         .collect(Collectors.toList()));
     }
 
+    /**
+     * Maps linearly two lists.
+     *
+     * @param kl  the keys list
+     * @param vl  the values list
+     * @param <K> the key type
+     * @param <V> the value type
+     * @return the map
+     */
+    public static <K, V> Map<K, V> linearMap(List<K> kl, List<V> vl) {
+        if (Objects.isNull(kl) || Objects.isNull(vl) || kl.size() != vl.size())
+            throw new IllegalArgumentException();
+
+        return Collections.unmodifiableMap(IntStream
+                .range(0, kl.size()).mapToObj(i -> i)
+                .filter(i -> Objects.nonNull(vl.get(i)))
+                .collect(Collectors.toMap(kl::get, vl::get)));
+    }
+
+    /**
+     * Merges two maps Map<K1, IK> and Map<IK, V> -> Map<K1, V>.
+     *
+     * @param m1   key maps
+     * @param m2   values maps
+     * @param <K>  the keys type
+     * @param <IK> the intermediate keys type
+     * @param <V>  the values type
+     * @return the traversing map
+     */
+    public static <K, IK, V> Map<K, V> traverseMaps(Map<K, IK> m1, Map<IK, V> m2) {
+        return Collections.unmodifiableMap(m1.entrySet().stream()
+                .collect(Collectors.toMap(Map.Entry::getKey, e -> m2.get(e.getValue()))));
+    }
+
+    /**
+     * Returns an inverted copy of a bijective map.
+     *
+     * @param m   the map to invert
+     * @param <K> the keys type
+     * @param <V> the values type
+     * @return the inverted map
+     */
+    public static <K, V> Map<K, V> invertMap(Map<V, K> m) {
+        return Collections.unmodifiableMap(m.entrySet().stream()
+                .collect(Collectors.toMap(Map.Entry::getValue, Map.Entry::getKey)));
+    }
+
 }