Directed Graph Traversal using recursive DFS

import java.util.Stack;



public class RecursiveDFS {



    public static int graph[][] = {



            { 1, 2 },// 0



            { 0, 3, 4 },// 1



            { 0, 5, 6 },// 2



            { 1, 7 },// 3



            { 1, 7 },// 4



            { 2, 7 },// 5



            { 2, 7 },// 6



            { 3, 4, 5, 6 } // 7



    };



    static int visited[] = { -1, -1, -1, -1, -1, -1, -1, -1 };// Initialize all

                                                                // unvisited.



    public static int[] findNeighbours(int v) {



        return graph[v];



    }



    public static boolean isVisited(int v) {

        if (visited[v] == 1)

            return true;

        else

            return false;

    }



    public static void recursiveDFS(int vertex) {

        System.out.print(vertex);

        visited[vertex] = 1;

        int neighbours[] = findNeighbours(vertex);

        for (int i = 0; i < neighbours.length; i++) {

            if (!isVisited(neighbours[i])) {

                recursiveDFS(neighbours[i]);

            }

        }



    }



    public static void main(String[] args) throws InterruptedException {

        recursiveDFS(0);

    }



}

DFS(Depth First Search) using a stack with adjacency list

import java.util.Stack;



import sun.misc.Queue;



public class DFS {

   

    public static int graph [][] = {

        {1,2},//0

        {0,3,4},//1

        {0,5,6},//2

        {1,7},//3

        {1,7},//4

        {2,7},//5

        {2,7},//6

        {3,4,5,6}//7

    };

   

    static Stack stack = new Stack();

    static Queue outPut = new Queue();

    static int visited [] = {-1,-1,-1,-1,-1,-1,-1,-1};//Initialize all unvisited.

   

    public static int [] findNeighbours(int v){

        return graph[v];

    }

   

    public static boolean isVisited(int v){

            if(visited[v]==1){

                return true;

            }else{

                return false;

            }

    }

   

    public static void main(String[] args) throws InterruptedException{

        stack.push(0);

        while(!stack.empty()){

            int vertex = (Integer)stack.pop();

            if(!isVisited(vertex)){

                visited[vertex]=1;

                outPut.enqueue(vertex);

                int neighbours []= findNeighbours(vertex);

                for(int i = 0 ;i<neighbours.length;i++){

                    if(!isVisited(neighbours[i])){

                        stack.push(neighbours[i]);

                    }

                }

               

            }

           

        }

       

        while(!outPut.isEmpty()){

            System.out.print(outPut.dequeue());

        }

       

    }

   

   



}

BFS

Android preference demo (Android 偏好設定)

Shared Preferences是用來儲存應用程式設定值的好用類別.

資料會一直存活在系統,直到應用程式被移除.

透過access preference name, 可以對資料做接收或者是寫入的動作.

範例如下.

========================
AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.cookbook.activity_lifecycle"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        
        <activity android:name=".PreferenceDemo"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
       
    </application>

</manifest>

PreferenceDemo.java

import com.cookbook.activity_lifecycle.R;

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class PreferenceDemo extends Activity{
    
    public static final String PREFS_NAME = "ap_settings";
    
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.pref) ;
        final Button setbutton = (Button) findViewById(R.id.setButton);
        setbutton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                EditText et = (EditText)findViewById(R.id.editText1);
                SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
                SharedPreferences.Editor editor = settings.edit();
                editor.putString("edit_text", et.getText().toString());
                // Commit the edits!
                editor.commit();
                et.setText("");
            }
        });
        
        final Button getButton = (Button) findViewById(R.id.getButton);
        getButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                EditText et = (EditText)findViewById(R.id.editText1);
                SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
                et.setText(settings.getString("edit_text", null));
            }
        });
    }

}

pref.xml

<?xml version="1.0" encoding="UTF-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <EditText
            android:id="@+id/editText1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:ems="10" 
            android:text="null"/>

        <Button
            android:id="@+id/setButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Set" />

        <Button
            android:id="@+id/getButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Get" />

    </LinearLayout>

Reference:Android Data Storage