Graphs

README.md

@@ -0,0 +1,3 @@
+# AlgorithmsAndDataStructures
+1. Реализовать программу, в которой задается граф из 10 вершин.
+Задать ребра и найти кратчайший путь с помощью поиска в ширину.

src/algorithmsAndDataStructures/BreadthFirstPath.java

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+package algorithmsAndDataStructures;
+
+import java.util.LinkedList;
+
+public class BreadthFirstPath {
+
+    private boolean[] marked;
+    private int[] edgTo;
+    private int source;
+
+    public BreadthFirstPath(Graph graph, int source) {
+        this.source = source;
+        marked = new boolean[graph.getVertexCount()];
+        edgTo = new int[graph.getVertexCount()];
+        bfs(graph, source);
+    }
+
+    private void bfs(Graph graph, int source) {
+        LinkedList<Integer> queue = new LinkedList<>();
+        queue.add(source);
+        marked[source] = true;
+        while (!queue.isEmpty()) {
+            int vertex = queue.removeFirst();
+            for (int w : graph.getAdjLists(vertex)) {
+                if (!marked[w]) {
+                    marked[w] = true;
+                    edgTo[w] = vertex;
+                    queue.addLast(w);
+                }
+            }
+        }
+    }
+
+
+    public boolean hasPathTo(int v) {
+        return marked[v];
+    }
+
+    public LinkedList<Integer> pathTo(int v) {
+        if (!hasPathTo(v)) {
+            return null;
+        }
+        LinkedList<Integer> stack = new LinkedList<>();
+        int vertex = v;
+        while (vertex != source) {
+            stack.push(vertex);
+            vertex = edgTo[vertex];
+        }
+        return stack;
+    }
+}

src/algorithmsAndDataStructures/DepthFirstPath.java

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+package algorithmsAndDataStructures;
+
+import java.util.LinkedList;
+
+public class DepthFirstPath {
+    private boolean[] marked;
+    private int[] edgTo;
+    private int source;
+
+    public DepthFirstPath(Graph graph, int source) {
+        this.source = source;
+        marked = new boolean[graph.getVertexCount()];
+        edgTo = new int[graph.getVertexCount()];
+        dfs(graph, source);
+
+    }
+
+    private void dfs(Graph graph, int v) {
+        marked[v] = true;
+        for (int w : graph.getAdjLists(v)) {
+            if (!marked[w]) {
+                edgTo[w] = v;
+                dfs(graph, w);
+            }
+        }
+    }
+
+    public boolean hasPathTo(int v) {
+        return marked[v];
+    }
+
+    public LinkedList<Integer> pathTo(int v){
+        if (!hasPathTo(v)){
+            return null;
+        }
+        LinkedList<Integer>stack=new LinkedList<>();
+        int vertex=v;
+        while (vertex!=source){
+            stack.push(vertex);
+            vertex=edgTo[vertex];
+        }
+        return stack;
+    }
+}

src/algorithmsAndDataStructures/Graph.java

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+package algorithmsAndDataStructures;
+
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+
+public class Graph {
+    private int vertexCount;
+    private int edgeCount;
+    private LinkedList<Integer>[] adjLists;
+
+    public Graph(int vertexCount) {
+        if (vertexCount < 1) {
+            throw new IllegalArgumentException("vertexCount: " + vertexCount);
+        }
+        this.vertexCount = vertexCount;
+        adjLists = new LinkedList[vertexCount];
+        for (int i = 0; i < adjLists.length; i++) {
+            adjLists[i] = new LinkedList<>();
+        }
+    }
+
+    public int getVertexCount() {
+        return vertexCount;
+    }
+
+    public int getEdgeCount() {
+        return edgeCount;
+    }
+
+    public List<Integer> getAdjLists(int vertex) {
+        return Collections.unmodifiableList(adjLists[vertex]);
+    }
+
+    public void addEdge(int v1, int v2) {
+        if (v1 < 0 || v2 < 0 || v1 > vertexCount || v2 > vertexCount) {
+            throw new IllegalArgumentException("");
+        }
+        adjLists[v1].add(v2);
+        if (v1 != v2) {
+            adjLists[v2].add(v1);
+        }
+    }
+}

src/algorithmsAndDataStructures/Main.java

@@ -3,6 +3,19 @@
 public class Main {
 
     public static void main(String[] args) {
-	// write your code here
+        Graph graph = new Graph(10);
+        graph.addEdge(1, 2);
+        graph.addEdge(2, 3);
+        graph.addEdge(3, 4);
+        graph.addEdge(5, 6);
+        graph.addEdge(2, 5);
+        graph.addEdge(7, 6);
+        graph.addEdge(8, 1);
+        graph.addEdge(2, 9);
+
+        BreadthFirstPath bfp = new BreadthFirstPath(graph, 1);
+        System.out.println(bfp.pathTo(7));
+
+
     }
 }