Equifax Breach

Equifax Breach

Presentation On Equifax Breach



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P ,NP , NP-Complete , NP-hard

I assume that you are looking for intuitive definitions, since the technical definitions require quite some time to understand. First of all, let's remember a preliminary needed concept to understand those definitions.

• Decision problem: A problem with a yes or no answer.

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Now, let us define those complexity classes.

P

P is a complexity class that represents the set of all decision problems that can be solved in polynomial time. That is, given an instance of the problem, the answer yes or no can be decided in polynomial time.

Example

Given a connected graph G, can its vertices be coloured using two colours so that no edge is monochromatic?

Algorithm: start with an arbitrary vertex, color it red and all of its neighbours blue and continue. Stop when you run out of vertices or you are forced to make an edge have both of its endpoints be the same color.

---

NP

NP is a complexity class that represents the set of all decision problems for which the instances where the answer is "yes" have proofs that can be verified in polynomial time.

This means that if someone gives us an instance of the problem and a certificate (sometimes called a witness) to the answer being yes, we can check that it is correct in polynomial time.

Example

Integer factorisation is in NP. This is the problem that given integers n and m, is there an integer f with 1 < f < m, such that f divides n (f is a small factor of n)?

This is a decision problem because the answers are yes or no. If someone hands us an instance of the problem (so they hand us integers n and m) and an integer f with 1 < f < m, and claim that f is a factor of n (the certificate), we can check the answer in polynomial time by performing the division n / f.

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NP-Complete

NP-Complete is a complexity class which represents the set of all problems X in NP for which it is possible to reduce any other NP problem Y to X in polynomial time.

Intuitively this means that we can solve Y quickly if we know how to solve X quickly. Precisely, Yis reducible to X, if there is a polynomial time algorithm f to transform instances y of Y to instances x = f(y) of X in polynomial time, with the property that the answer to y is yes, if and only if the answer to f(y) is yes.

Example

3-SAT. This is the problem wherein we are given a conjunction (ANDs) of 3-clause disjunctions (ORs), statements of the form

(x_v11 OR x_v21 OR x_v31) AND 
(x_v12 OR x_v22 OR x_v32) AND 
...                       AND 
(x_v1n OR x_v2n OR x_v3n)

where each x_vij is a boolean variable or the negation of a variable from a finite predefined list (x_1, x_2, ... x_n).

It can be shown that every NP problem can be reduced to 3-SAT. The proof of this is technical and requires use of the technical definition of NP (based on non-deterministic Turing machines). This is known as Cook's theorem.

What makes NP-complete problems important is that if a deterministic polynomial time algorithm can be found to solve one of them, every NP problem is solvable in polynomial time (one problem to rule them all).

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NP-hard

Intuitively, these are the problems that are at least as hard as the NP-complete problems. Note that NP-hard problems do not have to be in NP, and they do not have to be decision problems.

The precise definition here is that a problem X is NP-hard, if there is an NP-complete problem Y, such that Y is reducible to X in polynomial time.

But since any NP-complete problem can be reduced to any other NP-complete problem in polynomial time, all NP-complete problems can be reduced to any NP-hard problem in polynomial time. Then, if there is a solution to one NP-hard problem in polynomial time, there is a solution to all NP problems in polynomial time.

Example

The halting problem is an NP-hard problem. This is the problem that given a program P and input I, will it halt? This is a decision problem but it is not in NP. It is clear that any NP-complete problem can be reduced to this one. As another example, any NP-complete problem is NP-hard.

My favorite NP-complete problem is the Minesweeper problem.

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P = NP

This one is the most famous problem in computer science, and one of the most important outstanding questions in the mathematical sciences. In fact, the Clay Institute is offering one million dollars for a solution to the problem (Stephen Cook's writeup on the Clay website is quite good).

It's clear that P is a subset of NP. The open question is whether or not NP problems have deterministic polynomial time solutions. It is largely believed that they do not. Here is an outstanding recent article on the latest (and the importance) of the P = NP problem

Sample JDBC Connection Example JAVA,JDBC,MYSQL

/**
 * 
 */
package DatabaseConnection;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;


/**
 * @author satyanarayanagokavarapu
 *
 */
public class MySqlConnectionExample {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  // creates three different Connection objects
  Connection conn2 = null;

  try {

   String url2 = "jdbc:mysql://localhost:3306/soccer?
   user=root&password=mysql123";
   conn2 = DriverManager.getConnection(url2);
   if (conn2 != null) {
    System.out.println("Connected to the database soccer");
   }
  } catch (SQLException ex) {
   System.out.println("An error occurred. Maybe user/password is
 invalid");
   ex.printStackTrace();
  }
 }

}

MYSQL - SELECT Database

1. Open your terminal. 

2. Connect to MySql.If not use below link to know how to connect.

How to Connect to MySql Database using MAC terminal

3. Once you logged into your mysql then type the below command 
to SELECT a database (OMS is database name).
mysql> use OMS;
Database changed;

Which says Database 'OMS' is selected.

4. To check whether Database OMS selected or not type below 
command.
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| oms        |
+------------+
1 row in set (0.00 sec)

Which says Database 'OMS' is selected.

***********Happy Learning*************

MYSQL - Drop Database

1. Open your terminal. 

2. Connect to MySql.If not use below link to know how to connect.

How to Connect to MySql Database using MAC terminal

3. Once you logged into your mysql then type the below command 
to drop a database (OMS is database name).
mysql> drop DATABASE OMS;


4. To check whether Database OMS dropped or not type below 
command.
mysql> USE OMS;
ERROR 1049 (42000): Unknown database 'oms'

Which says Database 'OMS' no more exits.

***********Happy Learning*************

MYSQL - Create Database

1. Open your terminal. 

2. Connect to MySql.If not use below link to know how to connect.

How to Connect to MySql Database using MAC terminal

3. Once you logged into your mysql then type the below command 
to create a database.
mysql> CREATE DATABASE OMS;
Query OK, 1 row affected (0.00 sec)   
1 row affected means Database is created successfully.

4. To use this Database OMS type below command.
mysql> USE OMS;
Database changed

5. Check which database you are using by using below command.
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| oms        |
+------------+
1 row in set (0.00 sec)


***********Happy Learning*************

How to Connect to MySql Database using MAC terminal

1. Open your terminal. 

2. Check your current directory by typing pwd.
$ pwd

Output :
/usr/local/mysql/bin
your directory should be the bin folder of mysql else go to that 
directory by typing.
$ cd /usr/local/mysql/bin


3. When you are in mysql bin folder login to your mysql database 
using below command and enter password.
$ ./mysql -u root -p
Enter password: 
Output :

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 93
Server version: 5.7.19 MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. 
All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input 
statement.

mysql>    

If you see above welcome message then you are logged in to your mysql database.