Add implementation

Author: BNAndras

exercises/practice/relative-distance/.meta/src/reference/java/RelativeDistance.java

@@ -1,13 +1,68 @@
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Queue;
 
 class RelativeDistance {
 
+    private final Map<String, HashSet<String>> Graph;
+
     RelativeDistance(Map<String, List<String>>  familyTree) {
-        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+        final HashMap<String, HashSet<String>> graph = new HashMap<>();
+
+        for (Map.Entry<String, List<String>> entry : familyTree.entrySet()) {
+            String parent = entry.getKey();
+            List<String> children = entry.getValue();
+
+            graph.putIfAbsent(parent, new HashSet<>());
+
+            for (String child : children) {
+                graph.putIfAbsent(child, new HashSet<>());
+
+                graph.get(parent).add(child);
+                graph.get(child).add(parent);
+
+                for (String sibling : children) {
+                    if (!sibling.equals(child)) {
+                        graph.get(child).add(sibling);
+                    }
+                }
+            }
+        }
+
+        Graph = graph;
     }
 
     int degreeOfSeparation(String personA, String personB) {
-        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+        if (!Graph.containsKey(personA) || !Graph.containsKey(personB)) {
+            return -1;
+        }
+
+        Queue<String> queue = new LinkedList<>();
+        Map<String, Integer> distances = new HashMap<>() {
+            {
+                put(personA, 0);
+            }
+        };
+        queue.add(personA);
+
+        while (!queue.isEmpty()) {
+            String current = queue.poll();
+            int currentDistance = distances.get(current);
+
+            for (String relative : Graph.get(current)) {
+                if (!distances.containsKey(relative)) {
+                    if (relative.equals(personB)) {
+                        return currentDistance + 1;
+                    }
+                    distances.put(relative, currentDistance + 1);
+                    queue.add(relative);
+                }
+            }
+        }
+
+        return -1;
     }
 }