Notes, summaries, assignments, exams, and problems for Computers

Essential Algorithms and Data Structures

Longest Increasing Subsequence (LIS):

• Subproblem: dp[i] = length of LIS ending at index i
• Recursion: dp[i] = max(dp[j] + 1 for j < i and arr[j] < arr[i])
• Base case: dp[i] = 1 (every element is a subsequence of length 1)
• Time Complexity: O(n^2), O(n log n) with binary search optimization.

Longest Alternating Subsequence (LAS):

• Subproblem: dp[i][0] (increasing), dp[i][1] (decreasing)
• Recursion: dp[i][0] = max(dp[j][1] + 1 for j < i and arr[j] < arr[i]), dp[i][1] = max(dp[j][0] + 1 for j < i and arr[j] > arr[i])
• Base case: dp[0][0] = 1, dp[0][1] = 1
• Time Complexity: O(n^2)

0/1 Knapsack Problem:

• Subproblem: dp[i][w] = maximum value for the first i items and weight limit w
• Recursion: dp[i][w] = max(

Arithmetic Mean

The following C++ code calculates the arithmetic mean of numbers from 1 to n:

int main() {
    int n;
    double suma = 0;
    cout << "Vnesi broj: ";
    cin >> n;
    if (n <= 0) {
        cout << "Brojot na elementi mora da bide pogolem od 0!" << endl;
        return 1;  
    }
    for (int i = 1; i <= n; i++) {
        suma += i;  
    }
    double sredina = suma / n;
    cout << "Aritmetichkata sredina na broevite od 1 do " << n << " e: " << sredina << endl;
    return 0;
}

Sum

The following C++ code calculates the sum of numbers from 1 to n:

int main() {
    int n, sum = 0;
    cout << "Vnesi broj n: ";
    cin >> n;
    for (int i = 1; i <= n; i++)

Linux File System Structure: An archive of Linux is associated with 3 parts: superblock, inode table, and data blocks.

Network Ports: To see the ports assigned to services.

Display Active TCP/IP Connections: netstat -a

User Management:

• Create password: passwd (user)
• Add user to group: usermod -g group_name
• Disable: 60001
• Enable: 60002

Practical Commands:

Add User: adduser

1. Change folder privileges: chmod
2. Check privileges: ls -de (see if you changed privileges)

1. Create a user: useradd newuser
passwd newuser
2. Create a directory: The command mkdir is used to create directories:
   mkdir mydirectory
3. Create a report: ps -aux >> reporte.txt
4. Directories associated with the user: -d dirname
5. Changing permission: chmod 744 file.txt /file.txt
6. Change owner: chown
   Entering

Ejercicio de descuentos:

#!/bin/bash

read -p "¿Desea el billete también de vuelta? (s/n): " idavuelta

until [ $idavuelta=="s" ] || [ $idavuelta=="n" ]; do

read -p "¿Desea el billete también de vuelta? (s/n): " idavuelta

done

read -p "¿Tiene carnet joven? (s/n): " carnetjoven

until [ $carnetjoven="s" ] || [ $carnetjoven="n" ]; do

read -p "¿Tiene carnet joven? (s/n): " carnetjoven

done

descuento=0 billete=20

if [ $idavuelta="s" ]; then

descuento=20

billete=" expr $billete \* 2'

fi

if [ $carnetjoven="s" ]j then

descuento=30

fi

costefinal=`expr $billete \* \( 100 - $descuento \) / 100`

echo "El precio final del billete es $costefinal"

Ejercicio de medias:

#!/bin/bash

acu=0

cont=0

read -p "Introduce un numero: " num

while [ $num -ne 0 ]; do

acu=`expr $acu + $num`

cont=... Continue reading "Shell script" »

Kako si lep danes 

What is Lorem Ipsum?

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.

What is Lorem Ipsum?

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard... Continue reading "dsdfs" »

Programming Fundamentals

What is a Constant?

A constant is a data value that remains unchanged during the execution of a program.

Three Programming Constructs

The three fundamental programming constructs are: selection, iteration, and sequence.

Logical Operators

One example of a logical operator is AND.

• Operator: and
• Description: Logical AND: True if both operands are true.
• Syntax: x and y

Functions vs. Procedures

Difference: A function is typically used to calculate a value from a given input, while a procedure is a set of commands executed in a specific order.

Similarity: Functions must return a value, but in stored procedures, it is optional. Procedures can return zero or multiple values. Functions usually have only input parameters, whereas procedures... Continue reading "Programming Concepts: Constants, Constructs, and Operators" »

Arithmetic Operations in Java

Input Form

<% String num1Str = request.getParameter("num1"); String num2Str = request.getParameter("num2"); String operation = request.getParameter("operation"); if (num1Str != null && num2Str != null && !num1Str.isEmpty() && !num2Str.isEmpty() && operation != null) { double num1 = Double.parseDouble(num1Str); double num2 = Double.parseDouble(num2Str); double result = 0; switch (operation) { case "add": result = num1 + num2; out.println("

Result: " + result + "

"); break; case "subtract": result = num1 - num2; out.println("

Result: " + result + "

"); break; case "multiply": result = num1 * num2; out.println("... Continue reading "Java Arithmetic Operations Web App" »

HOSTàROUTER: 1

ENABLE

CONFIGURE TERMINAL

INTERFACE GIGABITETHERNET 0/0

IP ADDRESS 192.168.1.126 255.255.255.224

NO SHUTDOWN

EXIT

INTERFACE GIGABITEETHERNET 0/1

IP ADDRESS 192.168.1.158 255.255.255.240

NO SHUTDOWN

HOSTàSWITCH 2

ENABLE

CONFIFURE TERMINAL

INTERFACE VLAN 1

IP ADDRESS 192.168.1.157 255.255.255.240

NO SHUTDOWN

HOST/ROUTER 3

EXIT (LLEGAR AL CONFIGURE TERMINAL)

HOSTNAME MIDDLE

ENABLE SECRET CISCO

LINE CONSOLE 0

PASSWORD CLASS

LOGIN

EXIT

SECURITY PASSWORD MIN-LENGTH 10

SERVICE PASSWORD ENCRYPTION

IP DOMAIN-NAME CISCO

CRYPTON KEY GENERATE RSA

1024

EXIT

USERNAME CICLOS

LINE VTY 0 4

LOGIN LOCAL

TRANSPORT INPUT SSH

EXIT

INTERFACE GIBABITEETHERNET 0/0

IPV6 ADDRESS 2001:DB8:ACAD:A::1/64

IPV6 ADDRESS FE80::1 LIN

EXIT

GIBABITETHERNET 0/1

IPV6 ADDRESS 2001:DB8:ACAD:B::1/64

IPV6