强连通分量算法

Kosaraju算法 ，Targen算法(递归) c#

1

  1 /* 
  2  * User: Answer
  3  * Date: 2010-04-13
  4  * Time: 21:58
  5  */
  6 using System;
  7 using System.IO;
  8 using System.Collections;
  9 using System.Text;
 10 
 11 namespace Graph
 12 {
 13     /// <summary>
 14     /// Description of SCCKosaraju.
 15     /// </summary>
 16     public class SCCKosaraju
 17     {
 18         ArrayList[] adja; // adjacency list
 19         ArrayList[] Radja; // reverse adjacency list
 20         bool[] visited;
 21         Stack stack;
 22         int count = 1;
 23         
 24         public SCCKosaraju(ArrayList[] adja)
 25         {
 26             this.adja = adja;
 27             this.Radja = ReverseAdjacencyList(adja);
 28             this.stack = new Stack();
 29             visited = new bool[adja.Length];
 30                 
 31         }
 32         private ArrayList[] ReverseAdjacencyList(ArrayList[] adja)
 33         {
 34             ArrayList[] r = new ArrayList[adja.Length];
 35             for(int i=0;i<adja.Length;i++) {
 36                 foreach(int node in adja[i]) {
 37                     if(r[node] == null)
 38                         r[node] = new ArrayList();
 39                     r[node].Add(i);
 40                 }
 41             }
 42             return r;
 43             
 44         }
 45         
 46         public void DFS ( int node )
 47         {
 48             visited[node] = true;    
 49             foreach(int nei in adja[node]) {
 50                 if(!visited[nei]){
 51                     
 52                     DFS(nei);
 53                 }
 54             }
 55             stack.Push(node);
 56             
 57         }
 58 
 59         public void DFS2 ( int node )
 60         {
 61             visited[node] = true;
 62             Console.WriteLine("{0}:{1}",node,count);
 63             foreach(int nei in Radja[node] ) {
 64                 if(!visited[nei]) { 
 65                     
 66                     DFS2(nei);
 67                 }
 68             }
 69         }
 70 
 71         public void start ()
 72         {
 73             
 74             for(int i = 0;i<adja.Length;i++){
 75                 if ( !visited[i]) 
 76                     DFS(i);
 77             }
 78             
 79             Array.Clear(visited,0,visited.Length);
 80             
 81             while(stack.Count != 0) {
 82                 int node = (int)stack.Pop();
 83                 if(!visited[node]) {
 84                     DFS2(node);
 85                     count++;
 86                 }
 87             }
 88         }
 89                 public static void Main(string[] args)
 90         {
 91             ArrayList l1 = new ArrayList(){1,2};
 92             ArrayList l2 = new ArrayList(){3};
 93             ArrayList l3 = new ArrayList(){3,4};
 94             ArrayList l4 = new ArrayList(){0,5};
 95             ArrayList l5 = new ArrayList(){5};
 96             ArrayList l6 = new ArrayList(){};
 97             ArrayList[] edge = new ArrayList[]{l1,l2,l3,l4,l5,l6};
 98             
 99             new SCCKosaraju(edge).start();
100             Console.Write("END. ");
101             Console.ReadKey(true);
102         }
103 
104     }
105 }
106 

 

 

2

 

/* 
 * User: Answer
 * Date: 2010-04-12
 * Time: 21:53
 *
 */
using System;
using System.Collections;
using System.IO;

namespace Graph
{
    /// <summary>
    /// Description of SCC.
    /// </summary>
    public class SCCTargen
    {
        private int[] SCCnum;
        private int[] index;
        private int[] back;
        private Stack stack;
        private ArrayList[] adja;
        
        private int step = 1;
        private int count = 1;
        
        public SCCTargen(ArrayList[] adja)
        {
            this.adja = adja;
            this.index = new int[adja.Length];
            this.back = new int[adja.Length];
            this.SCCnum = new int[adja.Length];
            stack = new Stack();
        }
        public void start()
        {
            for(int i=0;i<index.Length;i++) {
                if(index[i] == 0)
                    Targen(i);
            }
            // Save the results
            //StreamWriter w = new StreamWriter("");
            for(int i=0;i<SCCnum.Length;i++) {
                Console.WriteLine("NODE {0} :{1} ",i+1,SCCnum[i]);
            }
        }
        public void Targen(int node)
        {
            stack.Push(node);
            
            index[node] = step;
            back[node]  = step++;
            foreach(int nei in (ArrayList)adja[node]) {
                
                if(index[nei] == 0 ) { //neighbor isnot visited
                    Targen(nei);
                    if(back[node] > back[nei])
                        back[node] = back[nei];
                } else if(stack.Contains(nei)){
                    if(index[nei] < back[node])
                        back[node] = index[nei];
                }
            }
            
            if(index[node] == back[node]) {
                int x = 0;
                do{
                    x = (int)stack.Pop();
                    SCCnum[x] = count;
                }while(x != node);
                count ++;
            }
            

        }
                 public static void Main(string[] args)
        {
            ArrayList l1 = new ArrayList(){1,2};
            ArrayList l2 = new ArrayList(){3};
            ArrayList l3 = new ArrayList(){3,4};
            ArrayList l4 = new ArrayList(){0,5};
            ArrayList l5 = new ArrayList(){5};
            ArrayList l6 = new ArrayList(){};
            ArrayList[] edge = new ArrayList[]{l1,l2,l3,l4,l5,l6};
                        new SCCTargen(edge).start();
            Console.Write("Press any key to continue . . . ");
            Console.ReadKey(true);
        }
    }
}