Merge remote-tracking branch 'upstream/master'

Author: SmartyAnsh

algorithms-miscellaneous-1/README.md

@@ -7,8 +7,6 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 
 - [Validating Input With Finite Automata in Java](https://www.baeldung.com/java-finite-automata)
 - [Example of Hill Climbing Algorithm](https://www.baeldung.com/java-hill-climbing-algorithm)
-- [Monte Carlo Tree Search for Tic-Tac-Toe Game](https://www.baeldung.com/java-monte-carlo-tree-search)
-- [Binary Search Algorithm in Java](https://www.baeldung.com/java-binary-search)
 - [Introduction to Minimax Algorithm](https://www.baeldung.com/java-minimax-algorithm)
 - [How to Calculate Levenshtein Distance in Java?](https://www.baeldung.com/java-levenshtein-distance)
 - [How to Find the Kth Largest Element in Java](https://www.baeldung.com/java-kth-largest-element)

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/Graph.java

@@ -0,0 +1,30 @@
+package com.baeldung.algorithms.astar;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+
+public class Graph<T extends GraphNode> {
+    private final Set<T> nodes;
+
+    private final Map<String, Set<String>> connections;
+
+    public Graph(Set<T> nodes, Map<String, Set<String>> connections) {
+        this.nodes = nodes;
+        this.connections = connections;
+    }
+
+    public T getNode(String id) {
+        return nodes.stream()
+            .filter(node -> node.getId().equals(id))
+            .findFirst()
+            .orElseThrow(() -> new IllegalArgumentException("No node found with ID"));
+    }
+
+    public Set<T> getConnections(T node) {
+        return connections.get(node.getId()).stream()
+            .map(this::getNode)
+            .collect(Collectors.toSet());
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/GraphNode.java

@@ -0,0 +1,5 @@
+package com.baeldung.algorithms.astar;
+
+public interface GraphNode {
+    String getId();
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/RouteFinder.java

@@ -0,0 +1,66 @@
+package com.baeldung.algorithms.astar;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.Queue;
+import java.util.stream.Collectors;
+
+public class RouteFinder<T extends GraphNode> {
+    private final Graph<T> graph;
+    private final Scorer<T> nextNodeScorer;
+    private final Scorer<T> targetScorer;
+
+    public RouteFinder(Graph<T> graph, Scorer<T> nextNodeScorer, Scorer<T> targetScorer) {
+        this.graph = graph;
+        this.nextNodeScorer = nextNodeScorer;
+        this.targetScorer = targetScorer;
+    }
+
+    public List<T> findRoute(T from, T to) {
+        Map<T, RouteNode<T>> allNodes = new HashMap<>();
+        Queue<RouteNode> openSet = new PriorityQueue<>();
+
+        RouteNode<T> start = new RouteNode<>(from, null, 0d, targetScorer.computeCost(from, to));
+        allNodes.put(from, start);
+        openSet.add(start);
+
+        while (!openSet.isEmpty()) {
+            System.out.println("Open Set contains: " + openSet.stream().map(RouteNode::getCurrent).collect(Collectors.toSet()));
+            RouteNode<T> next = openSet.poll();
+            System.out.println("Looking at node: " + next);
+            if (next.getCurrent().equals(to)) {
+                System.out.println("Found our destination!");
+
+                List<T> route = new ArrayList<>();
+                RouteNode<T> current = next;
+                do {
+                    route.add(0, current.getCurrent());
+                    current = allNodes.get(current.getPrevious());
+                } while (current != null);
+
+                System.out.println("Route: " + route);
+                return route;
+            }
+
+            graph.getConnections(next.getCurrent()).forEach(connection -> {
+                double newScore = next.getRouteScore() + nextNodeScorer.computeCost(next.getCurrent(), connection);
+                RouteNode<T> nextNode = allNodes.getOrDefault(connection, new RouteNode<>(connection));
+                allNodes.put(connection, nextNode);
+
+                if (nextNode.getRouteScore() > newScore) {
+                    nextNode.setPrevious(next.getCurrent());
+                    nextNode.setRouteScore(newScore);
+                    nextNode.setEstimatedScore(newScore + targetScorer.computeCost(connection, to));
+                    openSet.add(nextNode);
+                    System.out.println("Found a better route to node: " + nextNode);
+                }
+            });
+        }
+
+        throw new IllegalStateException("No route found");
+    }
+
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/RouteNode.java

@@ -0,0 +1,67 @@
+package com.baeldung.algorithms.astar;
+
+import java.util.StringJoiner;
+
+class RouteNode<T extends GraphNode> implements Comparable<RouteNode> {
+    private final T current;
+    private T previous;
+    private double routeScore;
+    private double estimatedScore;
+
+    RouteNode(T current) {
+        this(current, null, Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY);
+    }
+
+    RouteNode(T current, T previous, double routeScore, double estimatedScore) {
+        this.current = current;
+        this.previous = previous;
+        this.routeScore = routeScore;
+        this.estimatedScore = estimatedScore;
+    }
+
+    T getCurrent() {
+        return current;
+    }
+
+    T getPrevious() {
+        return previous;
+    }
+
+    double getRouteScore() {
+        return routeScore;
+    }
+
+    double getEstimatedScore() {
+        return estimatedScore;
+    }
+
+    void setPrevious(T previous) {
+        this.previous = previous;
+    }
+
+    void setRouteScore(double routeScore) {
+        this.routeScore = routeScore;
+    }
+
+    void setEstimatedScore(double estimatedScore) {
+        this.estimatedScore = estimatedScore;
+    }
+
+    @Override
+    public int compareTo(RouteNode other) {
+        if (this.estimatedScore > other.estimatedScore) {
+            return 1;
+        } else if (this.estimatedScore < other.estimatedScore) {
+            return -1;
+        } else {
+            return 0;
+        }
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", RouteNode.class.getSimpleName() + "[", "]").add("current=" + current)
+            .add("previous=" + previous).add("routeScore=" + routeScore).add("estimatedScore=" + estimatedScore)
+            .toString();
+    }
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/Scorer.java

@@ -0,0 +1,5 @@
+package com.baeldung.algorithms.astar;
+
+public interface Scorer<T extends GraphNode> {
+    double computeCost(T from, T to);
+}

algorithms-miscellaneous-2/src/test/java/com/baeldung/algorithms/astar/underground/HaversineScorer.java

@@ -0,0 +1,19 @@
+package com.baeldung.algorithms.astar.underground;
+
+import com.baeldung.algorithms.astar.Scorer;
+
+public class HaversineScorer implements Scorer<Station> {
+    @Override
+    public double computeCost(Station from, Station to) {
+        double R = 6372.8; // In kilometers
+
+        double dLat = Math.toRadians(to.getLatitude() - from.getLatitude());
+        double dLon = Math.toRadians(to.getLongitude() - from.getLongitude());
+        double lat1 = Math.toRadians(from.getLatitude());
+        double lat2 = Math.toRadians(to.getLatitude());
+
+        double a = Math.pow(Math.sin(dLat / 2),2) + Math.pow(Math.sin(dLon / 2),2) * Math.cos(lat1) * Math.cos(lat2);
+        double c = 2 * Math.asin(Math.sqrt(a));
+        return R * c;
+    }
+}