52Java深度优先搜索实现

Posted 2021-04-11 菜鸟学编程

Java深度优先搜索实现

---

import java.util.*;

/**
 * Implementation of a Depth First Search
 *
 * @author Unknown
 *
 */

public class DFS{

    /**
     * Implementation in code of a DFS
     *
     * @param a structure to be DFS'ed
     * @param vertices The vertices
     * @param source The source
     */
    public static void dfsImplement(byte [][] a,int vertices,int source){            //passing adjacency matrix and no of vertices
        byte []b=new byte[vertices];               //flag container containing status of each vertices
        Arrays.fill(b,(byte)-1);                  //status initialization
        /*       code   status
                  -1  =  ready
                   0  =  waiting
                   1  =  processed       */


        Stack st=new Stack(vertices);         //operational stack
        st.push(source);                          //assigning source
        while(!st.isEmpty()){
            b[st.peek()]=(byte)0;                 //assigning waiting status
            System.out.println(st.peek());
            int pop=st.pop();
            b[pop]=(byte)1;                       //assigning processed status
            for(int i=0;i<vertices;i++){
                if(a[pop][i]!=0 && b[i]!=(byte)0 && b[i]!=(byte)1 ){
                    st.push(i);
                    b[i]=(byte)0;                  //assigning waiting status
                }}}

    }

    /**
     * The main method
     *
     * @param args Command line arguments
     */
    public static void main(String args[]){
        Scanner in=new Scanner(System.in);
        int vertices=in.nextInt(),source=in.nextInt();
        byte [][]a=new byte [vertices][vertices];
        //initially all elements of a are initialized with value zero

        for(int i=0;i<vertices;i++){
            int size =in.nextInt(); 
            for(int j=0;j<size;j++){
                a[i][in.nextInt()]=1;      //taking adjacency entries by assigning 1
            }
        }
        dfsImplement(a,vertices,source);         //function call
        in.close();
    }
}