Added solution to find the path in graph

YogenRaii · YogenRaii · commit 56817b668e2b · 2019-06-29T16:56:31.000-05:00
diff --git a/src/main/java/com/eprogrammerz/examples/algorithm/graphs/TestUndirectedGraph.java b/src/main/java/com/eprogrammerz/examples/algorithm/graphs/TestUndirectedGraph.java
@@ -3,8 +3,10 @@
 import org.junit.Test;
 
 import java.util.Arrays;
+import java.util.List;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 public class TestUndirectedGraph {
     @Test
@@ -15,7 +17,7 @@ public void testBFS() {
          *                  6
          *                /   \
          *               4     5
-         *             /  \     \
+         *             /  \  /  \
          *            1    2    3
          *
          */
@@ -26,10 +28,39 @@ public void testBFS() {
         Node d = new Node(4);
         d.connections = Arrays.asList(a, b);
         Node e = new Node(5);
-        e.connections = Arrays.asList(c);
+        e.connections = Arrays.asList(b, c);
         Node f = new Node(6);
         f.connections = Arrays.asList(d,e);
 
         assertEquals(2, graph.findNode(f, 2).id);
     }
+
+    @Test
+    public void testPath() {
+        /**
+         *
+         * /**
+         *                  6
+         *                /   \
+         *               4     5
+         *             /  \  /  \
+         *            1    2    3
+         *
+         */
+        UndirectedGraph graph = new UndirectedGraph();
+        Node a = new Node(1);
+        Node b = new Node(2);
+        Node c = new Node(3);
+        Node d = new Node(4);
+        d.connections = Arrays.asList(a, b);
+        Node e = new Node(5);
+        e.connections = Arrays.asList(b, c);
+        Node f = new Node(6);
+        f.connections = Arrays.asList(d, e);
+
+        List<Integer> actual = graph.findPath(f, 2);
+
+        List<List<Integer>> expected = Arrays.asList(Arrays.asList(6, 4, 2), Arrays.asList(6, 5, 2));
+        assertTrue(expected.contains(actual));
+    }
 }
diff --git a/src/main/java/com/eprogrammerz/examples/algorithm/graphs/UndirectedGraph.java b/src/main/java/com/eprogrammerz/examples/algorithm/graphs/UndirectedGraph.java
@@ -19,10 +19,6 @@ public Node findNode(Node start, int targetId) {
             throw new IllegalArgumentException("Graph should have at least one Node.");
         }
 
-        if (start.id == targetId) {
-            return start;
-        }
-
         Queue<Node> neighbors = new LinkedList<>();
         neighbors.add(start);
 
@@ -43,4 +39,36 @@ public Node findNode(Node start, int targetId) {
 
         return null;
     }
+
+    public List<Integer> findPath(Node start, int targetId) {
+        List<List<Integer>> paths = new ArrayList<>();
+        findPath(start, targetId, paths, new ArrayList<>());
+
+        List<Integer> shortest = paths.stream().min(Comparator.comparingInt(List::size)).orElse(null);
+        return shortest;
+    }
+
+    private void findPath(Node node, int end, List<List<Integer>> paths, List<Integer> temp) {
+        if (node == null) return;
+
+        temp.add(node.id);
+        node.visited = true;
+
+        if (node.id == end) {
+            paths.add(new ArrayList<>(temp));
+            return;
+        }
+
+        List<Node> neighbors = node.connections;
+
+        if (neighbors != null) {
+            for (Node neighbor: neighbors) {
+                if (!neighbor.visited) {
+                    findPath(neighbor, end, paths, temp);
+                    temp.remove(temp.size() - 1);
+                }
+            }
+        }
+
+    }
 }
