Notes, abstracts, papers, exams and problems of Computers

1. What is recurrence for worst case of QuickSort and what is the time complexity in Worst case? Recurrence is T(n) = T(n-1) + O(n) and time complexity is O(n^2) 2. Suppose we have a O(n) time algorithm that finds median of an unsorted array. Now consider a QuickSort implementation where we first find median using the above algorithm, then use median as pivot. What will be the worst case time complexity of this modified QuickSort. O(nLogn)  3. Given an unsorted array. The array has this property that every element in array is at most k distance from its position in sorted array where k is a positive integer smaller than size of array. Which sorting algorithm can be easily modified for sorting this array and what is the obtainable time complexity?

Explanation

10.1 Pivot tables

What is a pivot table? It is one of the most powerful tools in Excel. They are also called “dynamic” because the data on them can be changed by rearranging or changing the position of the column and row headers in an easy and quick way.

The use of a dynamic table is to obtain information summaries from our data grid in order to be able to quickly analyze big volumes of information. These type of tables can be used in situations such as:

• When you have a table with rows that have different date and you need to organize the information by time periods (month, semester, etc.)
• When you need to change the arrangement in the rows or column cells to show different perspectives from the same data set.

Follow these steps to... Continue reading "Excel Pivot Tables, Search and Logic Functions, Macros" »

Business Values of Telecom Standardization for Operators

1. Multiple sources of supply (decrease risk of sole supplier dependencies/lock-in, improve choice at competitive prices).
2. Interoperability, e.g., multi-vendor networks, service interop.
3. Assurance that investment in technology should not abruptly change or fail.

Business Values of Telecom Standardization for Vendors

1. Network vendors can sell to all service operators, freed from vendor-specific R&D.
2. Reduce customization.
3. Build reputation / customer confidence - strong standards brand.
4. Larger markets from wide adoption, greater economies of scale.

Types of Standards Bodies

1. Accredited
2. Treaty-based
3. Partnerships

Telecom Acronyms Explained

1. ITU: International Telecommunication Union
2. IETF: Internet Engineering

SQL*Plus is the version of SQL used to access Oracle databases

1.True

2.False

SQL*Plus del command can delete all lines from the buffer at once

1.True

2.False

There is no difference between the CHAR and VARCHAR2 data types. They are just spelled differently

1.True

2.False

Which command(s) set the title of SQL*Plus report

1. Set Headsep
2. Column
3. Set PageSize
4. Set Line Size
5. Edit
6. Define_Editor
7. Start
8. Remark
9. /* */
10. Host
11. Ttitle
12. Btitile
13. @
14. Break On
15. Compute Sum
16. Set NewPage
17. Set Pause
18. Save
19. Host
20. Command is not in the list
21. Command does not exist

Table in Oracle cannot be created if the primary key is not specified

1.True

2.False

Alternate key may contain NULL values

1.True

2.False

Table can have several alternate keys, but only one primary key and one foreign key

1.True

2.False

Which command(s) is/... Continue reading "SQL*Plus and Oracle Database: Test Questions and Answers" »

Python Store Management System

This code defines a Store class in Python, designed to manage customers, sellers, and orders. It uses basic object-oriented principles and data structures.

Class Definition

from Problema2.Cliente import Cliente
from Problema2.Vendedor import Vendedor

class Tienda():
    def __init__(self):
        self.__personas = []
        self.__pedidos = []

    def altaCliente(self, Cliente):
        alta = False
        if Cliente in self.__personas:
            alta = False
        else:
            self.__personas.append(Cliente)
            alta = True
        return alta

    def altaVendedor(self, Vendedor):
        alta = False
        if Vendedor in self.__personas:
            alta = False
        else:

Inheritance in Java

Inheritance in Java is a mechanism where one object acquires all the properties and behaviors of another object. Inheritance represents the IS-A relationship, also known as a parent-child relationship.

Using inheritance, you can create a general class that defines common traits for a set of related items. This class can then be inherited by other classes, each adding its unique elements.

The keyword extends defines a new class from an existing class. The existing class is called the parent/base/superclass, and the new class is called the child/derived/subclass.

Here's a breakdown:

• Child classes inherit all members of their parent class.
• Child classes cannot access the private members of the parent class directly.
• To access private

Map & Diccionarios

Import Statements

import java.security.InvalidParameterException;
import java.util.*;

RedCarreteras Class

public class RedCarreteras { 
    private Map<String, Map<String, Integer>> red;

    //CONSTRUCTORES
    public RedCarreteras() {
        red = new HashMap<>();// Nuevo dicc a 0
    }

    //METODOS
    private void validarTramo(String una, String otra, int distancia) {
        if (una == null || otra == null || una.equals(otra) || distancia < 1)
            throw new InvalidParameterException();
    }

    public Set<String> ciudades() {
        return red.keySet();
    }

    public int nuevoTramo(String una, String otra, int distancia) {
        validarTramo(una, otra, distancia);

RAM (Random Access Memory)

Random Access Memory is one of two basic types of memory. Portions of programs are stored in RAM when the program is launched so that the program will run faster. Though a PC has a fixed amount of RAM, only portions of it will be accessed by the computer at any given time. Also called memory.

Scrolling

Scrolling allows lines displayed on the screen to be moved up or down by one line as a new line is added and an existing one is removed.

Shooter

A shooter is a game whose main focus is combat involving guns or other projectile weapons such as missiles.

Shopping Cart

A shopping cart is software that keeps track of what you buy on a site.

Software Engineer

A software engineer is a person that writes computer programs.

Speech Recognition

Speech

1. Processes

A process is a program in execution. It is a unit of work within the system. A program is a passive entity, while a process is an active one. A process needs resources to accomplish its task (CPU, memory, I/O, files). Process termination requires the reclamation of any reusable resources. A single-threaded process has one program counter, specifying the location of the next instruction to execute. The process executes instructions sequentially, one at a time, until completion. A multithreaded process has one program counter per thread. Concurrency is achieved by multiplexing the CPUs among the processes or threads.

2. Process States

As a process executes, it changes its state:

• New: The process is being created.
• Running: Instructions