Notes, abstracts, papers, exams and problems of Computers

Understanding HashMaps in Python

Introduction

This document demonstrates a simple implementation of a HashMap in Python. A HashMap, also known as a hash table, is a data structure that implements an associative array abstract data type, a structure that can map keys to values. A hash function is used to compute an index into an array of buckets or slots, from which the desired value can be found.

Code Implementation

The following code provides a basic HashMap class in Python:

Loops

• // Loop forward
• for i in 0..
• // do something
• }
• // Loop in reverse
• for index in stride(from: 5, through: 1, by: -1) {
• print(index) // 5,4,3,2,1
• }
• // OR
• for i in (0..<10).reversed() {
• print(i)
• }

Strings

• // Convert String to Array of Strings containing 1 Character
• var strArr = str.characters.map { String($0) }
• // Join Array of Strings into 1 String
• var str = strArr.joined(separator: "")
• // Split String into array
• import Foundation
• let fullNameArr = fullName.components(separatedBy: " ")
• // Split String into Characters
• let subsequences = str.characters.split(separator: " ") // Returns array of Subsequence, not array of strings
• String(subsequences[0]) // to use as string
• // Convert String to Array of Characters
• sChars = Array(string.characters)

String/Character to

Internal transport

Refers to the physical movement of products inside loading/unloading areas, docks, order preparation zones, truck load and any other eventual activity that implies products movements inside the warehouse.

Horizontal transport:

On this type of transport merchandise do not need to be raised to locate in a determined place. (Pallet truck, roller conveyor, conveyor belt system, auto guide transport system).

Vertical transport:

This transport not just allows the product to be transported from one place to another, but also to be raised to locate in a specific place. (Conventional forklift, retractable forklift, trilateral forklift).

Conventional forklift/truck lift (“Toros”)

Could be fixed mast or counterbalance, they need from 3... Continue reading "Internal Transport and Storage Systems in Warehouses" »

Drawbacks of Classful Addressing

Subnets have a fixed number of host addresses, leading to many unused/wasted IP addresses.

Solutions for IP Address Shortages

Short-term: Classless addressing
Long-term: IPv6

CIDR (Classless Inter-Domain Routing)

CIDR uses a hierarchical addressing scheme based on VLSM (Variable Length Subnet Masking).

Advantages of CIDR

• Replaces classful addressing with a more flexible and less wasteful classless scheme.
• Enhances route aggregation.

How VLSM Works

VLSM further subnets existing subnets by taking bits from the host ID, creating a multi-level hierarchy with "sub-subnets."

Supernetting

Supernetting combines continuous network addresses into a new address defined by the subnet mask. Multiple networks are combined into a larger... Continue reading "Understanding CIDR, Subnetting, and Supernetting in IP Addressing" »

Verifying Text Summaries of Relational Data Sets

AggChecker

int opcion=0;

double cantidad, vuelto;

double pago, total = 0;

string[,] fruta = { { 'Manzana', '4.9' }, { 'Pera', '5.5' }, { 'Naranja', '8.6' }, { 'Platano', '2.7' } ,{ 'Fresa', '1.9' } ,{ 'Piña', '2.4' }, { 'Papaya', '4.2' }, { 'Sandia', '3.4' } ,{ 'Durazno', '3.5' } };

String[,] añaFruta = newString[50, 5];

int i=0, j=0;

int añadir = 0,tFruta=0;

do{

do{

i = 0;

Console.Write('_________________________ ' +

'FRUTERIA .... '+

'1) AÑADIR FRUTA. ');

while (i < 9)

{ Console.Write(i+2+') '+fruta[i,0]+' ');

i++;

}

if(añadir>0)

{j = 11;

i = 0;

tFruta = añadir+9;

while (i < añadir)

{Console.Write(j + ') ' + añaFruta[i, 0] + ' ');

j++;i++;

}

}

else { tFruta = 9; }

Console.Write(tFruta + 2+') Pagar. ');

opcion = int.Parse(Console.ReadLine(

Aggregate Functions

How many hotels are there?

SELECT COUNT(*) FROM Hotel;

What is the average price of a room?

SELECT AVG(price) FROM Room;

What is the total revenue per night from all double rooms?

SELECT SUM(price) FROM Room WHERE type = 'D';

How many different guests have made bookings for August?

SELECT COUNT(DISTINCT guestNo) FROM Booking WHERE (dateFrom <= DATE'2004-08-01' AND dateTo >= DATE'2004-08-01') OR (dateFrom >= DATE'2004-08-01' AND dateFrom <= DATE'2004-08-31');

Subqueries and Joins

List the price and type of all rooms at the Grosvenor Hotel.

SELECT price, type FROM Room WHERE hotelNo = (SELECT hotelNo FROM Hotel WHERE hotelName = 'Grosvenor Hotel');

List all guests currently staying at the Grosvenor Hotel.

SELECT * FROM Guest... Continue reading "SQL Queries and Data Modeling" »

Computer System

Components:

• CPU
• Memory (ROM/RAM)
• I/O unit

BCD (Binary-Coded Decimal)

• Add 0110 to the result if it falls between 1010 and 1111.

Overflow

• Occurs when both numbers being added are positive or negative, and the result exceeds the maximum representable value.

IEEE-754 Standard

• 32 bits: 1 sign bit, 8 exponent bits, 23 mantissa bits
• NAN (Not a Number): Represents an error, exponent with all 1s and a sign bit of 0.
• Always add trailing zeros to complete the required number of bits.

Decoder

• Converts input to output using 2^n AND gates.

Memory

• Components: Address, data, enable, read, write

Control Unit

• Hardware instruction logic
• Decodes and monitors the execution of instructions.

ALU (Arithmetic Logic Unit)

• Performs numerical and logical evaluations.
• Receives

Midterm Answers