51Java 广度优先搜索实现

Posted 2021-04-14 菜鸟学编程

Java 广度优先搜索实现

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import java.util.*;

/**
 * Implementation of a Breadth First Search
 *
 * @author Unknown
 *
 */
public class BFS{

    /**
     * The BFS implemented in code to use.
     *
     * @param a Structure to perform the search on a graph, adjacency matrix etc.
     * @param vertices The vertices to use
     * @param source The Source
     */
    public static void bfsImplement(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.peek();
            b[pop]=(byte)1;               //assigning processed status
            st.pop();                  //removing head of the queue
            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
            }
        }
        bfsImplement(a,vertices,source);         //function call
        in.close();
    }
}