dag

Author: iScript

.idea/workspace.xml

@@ -0,0 +1,7 @@
+5 6
+0 1
+1 2
+1 3
+2 4
+3 2
+3 0

g8.txt

@@ -7,6 +7,9 @@ public class CycleDetection {
     private boolean hasCycle = false;
 
     public CycleDetection(Graph G){
+        if(G.isDirected())
+            throw new IllegalArgumentException("只支持无向图");
+
         this.G = G;
         visited = new boolean[G.V()];
 
@@ -45,5 +48,9 @@ public static void main(String[] args){
         CycleDetection cycleDetection = new CycleDetection(g);
         System.out.println(cycleDetection.hasCycle());
 
+        Graph g2 = new Graph("g8.txt",true);
+        CycleDetection cycleDetection2 = new CycleDetection(g2);
+        System.out.println(cycleDetection2.hasCycle());
+
     }
 }

out/production/Graph/CycleDetection.class

@@ -0,0 +1,58 @@
+// 有向图的环检测
+public class DirectedCycleDetection {
+    private Graph G;
+    private boolean[] visited;
+    private boolean[] onPath;   //是否在当前搜索路径上
+    private boolean hasCycle = false;
+
+    public DirectedCycleDetection(Graph G){
+        if(!G.isDirected())
+            throw new IllegalArgumentException("只支持有向图");
+
+        this.G = G;
+        visited = new boolean[G.V()];
+        onPath = new boolean[G.V()];
+
+        // 多包一层for，防止有多个联通分量
+        for(int v = 0 ;v<G.V();v++){
+            if(!visited[v])
+                if(dfs(v,v)) {
+                    hasCycle = true;break;
+                }
+
+        }
+    }
+
+    // 从顶点v开始，判断图中是否有环
+    private boolean dfs(int v,int parent){
+        visited[v] = true;
+        onPath[v] = true;
+
+        // 遍历相邻节点
+        for(int w : G.adj(v)){
+            if(!visited[w]) {
+                if (dfs(w, v)) return true;           //
+            }else if( onPath[w])    // 判断是否有环：不是父级且在搜索路径上
+                    return true;
+        }
+
+        onPath[v] = false;
+
+        return false;
+    }
+
+    // 是否有环
+    public boolean hasCycle(){
+        return hasCycle;
+    }
+
+
+    public static void main(String[] args){
+
+
+        Graph g2 = new Graph("g8.txt",true);
+        DirectedCycleDetection cycleDetection2 = new DirectedCycleDetection(g2);
+        System.out.println(cycleDetection2.hasCycle());
+
+    }
+}

out/production/Graph/DirectedCycleDetection.class

@@ -9,8 +9,19 @@ public class Graph implements  Cloneable{
     private int V;  // 顶点
     private int E;  // 边
     private TreeSet<Integer>[] adj;    // 领接表
+    private  boolean directed;
+    private  int[] indegrees,outdegrees; // 有向图的出度和入度
+
+
+    // 默认无向图
+    public Graph(String filename){
+        this(filename,false);
+    }
+
+    // 更新支持有向图
+    public Graph(String filename,boolean directed) {
+        this.directed = directed;
 
-    public Graph(String filename) {
         File file = new File(filename);
         if(!file.exists()) throw new IllegalArgumentException("文件不存在");
 
@@ -24,6 +35,9 @@ public Graph(String filename) {
                 adj[i] = new TreeSet<Integer>();
             }
 
+            indegrees = new int[V];
+            outdegrees = new int[V];
+
             E = scanner.nextInt();          // 第一行的第二值个为边
             if(E < 0) throw new IllegalArgumentException("E must be non-negative");
             for(int i = 0; i < E; i ++){    //
@@ -34,7 +48,14 @@ public Graph(String filename) {
                 if(adj[a].contains(b)) throw new IllegalArgumentException("Parallel Edges are Detected!");  // 判断平行边
 
                 adj[a].add(b);
-                adj[b].add(a);
+                if(directed){
+                    // 统计入度和出度
+                    outdegrees[a]++;
+                    indegrees[b]++;
+                }
+
+                if(!directed)
+                    adj[b].add(a);
             }
         }
         catch(IOException e){
@@ -43,6 +64,9 @@ public Graph(String filename) {
 
     }
 
+    public boolean isDirected(){
+        return directed;
+    }
 
     public void validateVertex(int v){
         if(v < 0 || v >= V)
@@ -75,24 +99,50 @@ public Iterable<Integer> adj(int v) {
 
     // 返回一个顶点的度，即顶点相邻的点有几个
     public int degree(int v){
+        //如果是有向图
+        if(directed)
+            throw new IllegalArgumentException("只支持无向图");
         validateVertex(v);
         return adj[v].size();
     }
 
+    public int indegree(int v){
+        if(!directed)
+            throw new RuntimeException("indegree only works in directed graph.");
+        validateVertex(v);
+        return indegrees[v];
+    }
+
+    public int outdegree(int v){
+        if(!directed)
+            throw new RuntimeException("outdegree only works in directed graph.");
+        validateVertex(v);
+        return outdegrees[v];
+    }
+
 
     public void removeEdge(int v,int w){
         validateVertex(v);
         validateVertex(w);
 
+        if(adj[v].contains(w)){
+            E --;
+            if(directed){
+                indegrees[w] --;
+                outdegrees[v] --;
+            }
+        }
+
         adj[v].remove(w);
-        adj[w].remove(v);
+        if(!directed)
+            adj[w].remove(v);
     }
 
     @Override
     public String toString(){
         StringBuilder sb = new StringBuilder();
 
-        sb.append(String.format("V = %d, E = %d\n", V, E));
+        sb.append(String.format("V = %d, E = %d , directed = %b \n", V, E,directed));
         for(int i = 0; i < V; i ++){
             sb.append(String.format("%d :", i));
             for(int w : adj[i])
@@ -125,7 +175,10 @@ public Object clone(){
 
     public static void main(String[] args){
 
-        Graph graph = new Graph("g.txt");
+//        Graph graph = new Graph("g.txt");
+//        System.out.print(graph);
+
+        Graph graph = new Graph("g8.txt",true);
         System.out.print(graph);
     }
 }

out/production/Graph/Graph.class

@@ -10,8 +10,10 @@ public class WeightedGraph implements  Cloneable{
     private int V;  // 顶点
     private int E;  // 边
     private TreeMap<Integer,Integer>[] adj; //adj数组，里面保存着TreeMap。treemap参数 相邻的顶点 ，权值
+    private  boolean directed;
 
-    public WeightedGraph(String filename) {
+    public WeightedGraph(String filename,boolean directed) {
+        this.directed = directed;
         File file = new File(filename);
         if(!file.exists()) throw new IllegalArgumentException("文件不存在");
 
@@ -45,6 +47,13 @@ public WeightedGraph(String filename) {
 
     }
 
+    public WeightedGraph(String filename){
+        this(filename,false);
+    }
+
+    public boolean isDirected(){
+        return directed;
+    }
 
     public void validateVertex(int v){
         if(v < 0 || v >= V)
@@ -83,6 +92,7 @@ public int getWeight(int v,int w){
     }
 
     // 返回一个顶点的度，即顶点相邻的点有几个
+    // ?
     public int degree(int v){
         validateVertex(v);
         return adj[v].size();
@@ -119,7 +129,7 @@ public int degree(int v){
     public String toString(){
         StringBuilder sb = new StringBuilder();
 
-        sb.append(String.format("V = %d, E = %d\n", V, E));
+        sb.append(String.format("V = %d, E = %d , directed = %b \n", V, E,directed));
         for(int i = 0; i < V; i ++){
             sb.append(String.format("%d :", i));
             for(Map.Entry<Integer,Integer> entry : adj[i].entrySet() ) //遍历map