Add Dijkstras Algorithm

Author: rabestro

src/main/java/algorithm/Algorithm.java

@@ -3,5 +3,5 @@
 import java.util.List;
 
 public interface Algorithm<T> {
-    List<T> findRoute(Graph<T> graph, T source, T target);
+    List<T> findPath(Graph<T> graph, T source, T target);
 }

src/main/java/algorithm/Dijkstras.java

@@ -0,0 +1,37 @@
+package algorithm;
+
+import java.util.*;
+import java.util.stream.Stream;
+
+public class Dijkstras<T> implements Algorithm<T> {
+
+    @Override
+    public List<T> findPath(Graph<T> graph, T source, T target) {
+        final var queue = new LinkedList<T>();
+        final var visited = new HashSet<T>();
+        final var distances = new HashMap<T, Double>();
+        final var path = new HashMap<T, T>();
+        queue.add(source);
+
+        while (!queue.isEmpty()) {
+            final var previous = queue.pollFirst();
+            final var edges = graph.get(previous);
+            edges.forEach((node, time) -> {
+                final var distance = distances.getOrDefault(previous, .0) + time.doubleValue();
+                if (!visited.contains(node)) {
+                    queue.add(node);
+                    visited.add(node);
+                }
+                if (distance < distances.getOrDefault(node, Double.MAX_VALUE)) {
+                    path.put(node, previous);
+                    distances.put(node, distance);
+                }
+            });
+        }
+
+        final var route = new LinkedList<T>();
+        Stream.iterate(target, Objects::nonNull, path::get).forEach(route::addFirst);
+        return route;
+    }
+
+}