Subset with minimum length from an integer array that gives a given sum

In a given integer array finding subset with minimum elements that gives a sum.
For example in the given integer array

{110,13,21,31,64,12,6,7,99,10,23}

what are the subsets with minimum number of elements with sum 100. Following is the answer.

7 is the mimimum number of elements in a subset with sum 100
Subset:[31, 6, 7, 10, 12, 13, 21]

/*
 * Author: Ashok Kumar Chava
 */
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class SubsetFinder {
    public static void main(String s[]) {
        int arr[]={110,13,21,31,64,12,6,7,99,10,23};
        int k=100;
        boolean found=false;
        Arrays.sort(arr);
        System.out.println("Input array after sorting:"+Arrays.toString(arr));
        for(int i=1;i<arr.length;i++) {
            ArrayList<Integer> subSet=SubsetFinder.subSetFinder(arr,i,k);
            if(subSet!=null&&subSet.size()>0) {
                System.out.println(i+ " is the mimimum number of elements in a subset with sum "+k);
                System.out.println("Subset:"+subSet);
                found=true;
                break;
            }
        }
        if(found!=true) {
            System.out.println("There are no subsets that gives the sum "+k);
        }
    }
    public static ArrayList<Integer> subSetFinder(int[] arr,int subSetSize, int sum) {
        ArrayList<Integer> subList=new ArrayList<Integer>();
      
        for(int i=0;i<arr.length;i++) {
            subList=new ArrayList<Integer>();
            subList.add(arr[i]);
            int tempSum=arr[i];
            int goBack=0;
            if(tempSum==sum) {
                return subList;
              
            }
            for(int j=0;j<arr.length&&subList.size()<subSetSize;j++) {
                if(i!=j&&!subList.contains(arr[j])) {
                    tempSum=tempSum+arr[j];
                    subList.add(arr[j]);
                }
                if(tempSum==sum&&subList.size()==subSetSize) {
                  
                    return subList;
                  
                }else if(tempSum!=sum&&subList.size()==subSetSize){
                    if(j%subSetSize==0) {
                        goBack=1;
                    }else {
                        goBack=j%subSetSize;
                    }
                    tempSum=tempSum-subList.get(subList.size()-(goBack));
                    subList.remove(subList.size()-(goBack));
                }
            }
        }
        return null;
    }
}

Writing java client for Mongo DB

Following are the steps
1) Create a java project in one of the IDEs. I have used Eclipse.
2) Then add following libraries to the classpath
mongodb-driver-3.2.2.jar
mongodb-driver-3.2.2-javadoc.jar
bson-3.0.2.jar
mongodb-driver-async-3.2.2.jar
mongodb-driver-core-3.2.2.jar
mongo-java-driver-3.2.2.jar
All these libraries can be downloaded from the link here. If you like you can very well use maven instead of downloading.
3) Write a simple client code
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
public class MongoDBClient {
    public static void main(String[] args) throws Exception{
        MongoClient client = new MongoClient("localhost", 27017);
        MongoDatabase testDB = client.getDatabase("test");
     
        System.out.println("Dropping person collection in test database");
        MongoCollection<Document> collection = testDB.getCollection("person");
        collection.drop();
        System.out.println("Adding a person document in the person collection of test database");
        Document person = new Document("name", "Ashok Kumar Chava").append("age", 35).append("job", "none");
       
        collection.insertOne(person);
        person = new Document("name", "Advik Chava").append("age", 7).append("education", "PG");
        collection.insertOne(person);
        System.out.println("Now finding a persons using find");
        FindIterable<Document> persons = collection.find();
        MongoCursor<Document> personList=persons.iterator();
        while(personList.hasNext()){
            person=personList.next();
            System.out.printf("Person found, name is %s and age is %s education is %s job is %s\n", person.get("name"),
                    person.get("age"), person.get("education"), person.get("job"));
        }
        System.out.println("Closing client");
        client.close();
    }
}
4) Following will be the output of the above code
Adding a person document in the person collection of test database
Now finding a persons using find
Person found, name is Ashok Kumar Chava and age is 35 education is null job is none
Person found, name is Advik Chava and age is 7 education is PG job is null
Closing client
5) As you can see in the above code I have created a person Document and added few key values details to the Document. Also if you observe for the first person I completly ignored the eduction key value and for the second one I completely ignored the job key value. Then I am able to retrieve the values.
In the next section I will do some thing little more complicated.

Learning MongoDB - 1

 

MongoDB is a document oriented NOSQL DB. MongoDB supports linear scalability.

What is NOSQL DB?

In simple words nosql is nothing but non sql or non relational. Basically nosql DB allows storing and retrieving of non relational or tabular data. So this is quite opposite of what oracle and other RDBMS does.

Why we need NOSQL DB?

You can find lot of information in this page.

What is linear scalability?

Scalability is nothing but capacity of the system,network or process to handle more work. Linear scalability mens increase of the capcity of the syetem,process or network by adding more hardware instead of making changes at the code level.

What are the types of NOSQL DBs?

There are multiple types of NOSQL DBs like key-value stores, document databases, wide-column stores, and graph databases.

Where to download MongoDB for learning?

You can download it from this link.

Installing the mongoDB on windows?

Just double click the downloaded file and follow the instructions.

Starting mongoDB?

• First create a data folder for mongoDB. I have created mine as D:\MongoDB\data
• Also create a log folder mine is like D:\MongoDB\logs
• Create a config file under install directory, simple config file D:\MongoDB\Server\3.2\bin\first.cfg looks like

systemLog:
    destination: file
    path: D:\MongoDB\logs\mongod.log
storage:
    dbPath: D:\MongoDB\data

• Start MongoDB by going to command prompt and to the directory D:\MongoDB\Server\3.2\bin, there execute the command

mongod –config first.conf

• Check the log file to see if the mongod started propertly you should be seeing a message like “waiting for connections on port 27017”.
  

Connecting to MongoDB?

Execute the command “mongo” you will see the follwing prompt

D:\MongoDB\Server\3.2\bin>mongo
2016-07-13T09:44:22.613+0530 I CONTROL  [main] Hotfix KB2731284 or later update is installed, no need to zero-out data files
MongoDB shell version: 3.2.7
connecting to: test
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
        http://docs.mongodb.org/
Questions? Try the support group
        http://groups.google.com/group/mongodb-user
>

Also the DB can be accessed using http://localhost:27017/test

This is end of part 1.

Next part covers programatic way to connect to MongoDB.

 

 

 

 

Android App Math Tables Skill Tester for Kids

A very simple app that helps kids to test their math table skills. I have created this app for my son, try this and let me know what you think of this app

https://drive.google.com/file/d/0Bx6AtshoCkDjUHVGeFYtaTRRSHc/view?usp=sharing

New parties in AP

I don't understand why people launching parties in AP, after election notification issued. I guess they are not hoping to come to power for sure, but for something else. Kiran party is just there for splitting TDP votes and give benefit to Jagan&Congress. after election simply they are going to merge into congress.

I even know the line they will use at the time of merger, "As the state already split into to two, we think only a national party can do good for newly formed state"

Hope voters understand the purpose of these parties, and make a wise decision. :) :)

AAP’s success should only be the first step in new Indian politics.

Today AAP won confidence vote in assembly and now we all are eagerly waiting to see what difference they are going to make in politics. I hope people of this country and media will be patient with them, as they are the only hope we got in our corrupted and rotten political system. They should be given benefit of doubt in every aspect and should not be judged on daily basis, as now a days media is doing. At the same time AAP should restrain themselves from promoting a sponsor state instead they should concentrate on empowering people to fulfill their needs. 

Hope all goes well with AAP and for all of us. This new year brings  a new change to all of us.

Is Telangana state good for Telangana people?

First of all these are my personal opinions. I could be totally wrong with my predictions and in fact a lot of times I am wrong with my predictions.

So now is Telangana good for Telangana people? In simple words it may not be going to be as good as the politicians are trying to project it. Few reasons

- The GDP is going to be less than 50% of the existing combined state. So it may be difficult to fund all the existing schemes like aarogyasri.

- Immediate new investments to the Hyderabad going to be tough task. Creating new jobs in the state of Telangana for Telangana people is going to be a uphill task.

- Politicians promised a lot of things to Telangana people as part of making them participate in the movement, a lot of those promises are not even feasible like providing lot of govt. jobs. This may lead to unrest in the state. This may also lead to new lease of life to naxalism in the state.

- You love him or hate him KCR is the hero of the new Telangana state. He  may now change his plan to merge his party with congress. In that case too many political forces in Telangana will lead to lot of instability, which I think is not going to be good for a new state.

- If TRS merged into congress, then BJP is going to improve voter base in the new Telangana state and that may lead to new conflict between BJP and MIM.  May be lot of communal issues.

- I think its going to be a tough task to control hate politics against Andhra people in Telangana.  One hate crime against other region people can screw up new state’s future.