Algorithm Introduction--kosaraju algorithm (strong connectivity)

Package Org.loda.graph;import org.loda.util.in;/** * * @ClassName: KOSARAJUSCC * @Description: Kosaraju Strong Connectivity Algorithm * * Understanding: Original G, inverse If a->b in the order order, then the inverse figure RG if there is also a->b, indicating that this is strongly connected. * In reverse diagram in accordance with the original sequence of the reverse order DFS, if you can search from a to B, then there must be a->b, which is bound to strong connectivity. and * Expand, a Dfs can find how much, it means that the strong connectivity component is how big, a total number of searches on behalf of a total of how many strong connectivity components * * @author minjun* @date May 24, 2015 PM 11:31:05 * */public class K OSARAJUSCC {//strong connect number private int count;//is accessed private boolean[] visited;//each element belongs to the strong connected component Idprivate int[] Id;public KOSARAJUSCC (Digraph g) {//Initialize int v=g.v (); visited=new boolean[v];id=new int[v];//get reverse post Deptfirstorder d=new Deptfirstorder (g);//Get the inverse graph of G digraph rg=g.reverse ();//dfsfor (int i:d.reversepost ()) {if (!visited[i]) {if (+)) according to the topological order of the reverse graph { DFS (I,RG);//DFS is completed once, indicating a strong connectivity component, count+1count++;}}} /** * * @Title: DFS * @Description: Depth First search * @param @param v* @param @param g settings file * @return void return type * @throws */p rivate void Dfs (int v, Digraph g) {visited[v]=true;id[v]=count;for (int W:g.adj (v)) {if (!visited[w]) {DFS (w, g);}}} /** * * @Title: Count * @Description: Number of strongly connected componentsVolume * @param @return Set file * @return int return type * @throws */public int count () {return count;} /** * * @Title: strongconnected * @Description: Determine whether two points are strongly connected * @param @param a * @param @param b* @param @return Setting file * @re Turn Boolean return type * @throws */public boolean strongconnected (int a,int b) {return id[a]==id[b];} /** * * @Title: ID * @Description: Identity of the strong connected component * @param @param a * @param @return set file * @return int return type * @throws */ public int ID (int a) {return id[a];} /** * * @Title: PRINTSCC * @Description: Print all strong connected components * @param settings file * @return void return type * @throws */public void print SCC () {stringbuilder[] sb=new stringbuilder[count];for (int i=0;i<sb.length;i++) {sb[i]=new StringBuilder ();} for (int i=0;i<id.length;i++) {sb[id[i]].append ("\ t" +i);} for (StringBuilder s:sb) {System.out.println ("Connected component:" +s.tostring ());}} public static void Main (string[] args) {Digraph d=new Digraph (New in ("F:\\ algorithm \\attach\\tinyDG.txt")); KOSARAJUSCC k=new KOSARAJUSCC (d); System.out.println ("Number of strongly connected components:" +k.count ());//print strong all connected components K.PRINTSCC ();}} 

The text data introduced are:

13
22
4 2
2 3
3 2
6 0
0 1
2 0
11 12
12 9
9 10
9 11
7 9
10 12
11 4
4 3
3 5
6 8
8 6
5 4
0 5
6 4
6 9
7 6

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Output content:

The number of strongly connected components is: 5 Connected components: 7 Connected components: 68 Connected Components: 9101112 Connected components: 02345 Connected components: 1

Algorithm Introduction--kosaraju algorithm (strong connectivity)