Basic programming course: Lesson #5 Control structures. Part 2. Cycles. [ESP-ENG]

josepha (77)in #devjr-s20w5 • 3 days ago

Hello Steemians, welcome to my post, and stay safe as you read through this post.

Edited with canvas

Explain the cycles in detail. What are they and how are they used? What is the difference between the While and Do-While cycle?

Cycles Simply put in a layman's understanding, cycles are programming constructs that are used to repeat a block of code multiple (many) times until a certain condition is met.

Cycles are mostly useful in tasks that involve repetition like iterating over elements in performing calculations or in a list repeatedly until a specific result is achieved. In other programming languages, cycles are also known as Loops in this post I believe using a loop in place or cycle is not a bad idea, haha the reason is for you to get exposure.

Types

For Cycles (Loops)

We can use this when the number of iterations is known beforehand.
We can use Iterates over a sequence, For example, a range of numbers, lists, or arrays.

for i in range(5):  # Loops from 0 to 4
    print(i)

The above code will print numbers from 0 to 4, as the loop runs 5 times.

While Cycle (Loop)

This repeats a block of code while a specified condition is True.
Also, the condition is checked before executing the loop body, so the loop does not execute if the condition is false from the beginning.

Example in Python program:

i = 0
while i < 5:
    print(i)
    i += 1

The above cycle will print numbers from 0 to 4, just like that of the for cycle (loop), but with a separate structure.

Do While Cycle (Loop): C++, and Java is the most supported languages for this.

The cycle body is executed at least once because the condition is checked after the cycle has been executed.
Example in C++

int i = 0;
do {
    cout << i << endl;
    i++;
} while (i < 5);

The above code will print numbers from 0 to 4, but the body will execute before the condition is checked which is the main difference.

Differences Between While and Do-While cycle

Based on Aspect	While	Do-While Cycle
Based on condition check	Before the cycle (loop) is executed	After the cycle (loop) is executes
Based on guaranteed executes	If the condition is false it may not execute	It executes at least once in respective of the condition.
Based language	C, JavaScript, Python, etc	Java, C, C++ etc.

Investigate how the Switch-case structure is used and give us an example

The Switch-case structure is a control flow statement that is used in programming to execute one block of code among several options which is based on the value of expression or a variable. It is another way of using multiple if-else statements, which makes the code more readable and cleaner when a programmer is checking for many conditions.

How The Switch-case Works

The statement evaluates an expression or a variable.
The case labels are what define possible values for expression, and the block of code under the matching case is executed.
The break statement is mostly added after each case to prevent the program from continuing to execute subsequent cases called "fall-through".
An optional default block can be added to handle cases where the default case value matches the variable or expression is not available.

Syntax (in C-like languages, such as C, C++, Java, and JavaScript):

switch (expression) {
    case value1:
        // Code to be executed if expression == value1
        break;
    case value2:
        // Code to be executed if expression == value2
        break;
    // You can have any number of case statements
    Default:
        // Code to be executed if the expression doesn't match any case
}

Example of a Switch-Case Structure (in C++)

#include <iostream>
using namespace std;

int main() {
    int day = 3;

    switch (day) {
        case 1:
            cout << "Monday" << endl;
            break;
        case 2:
            cout << "Tuesday" << endl;
            break;
        case 3:
            cout << "Wednesday" << endl;
            break;
        case 4:
            cout << "Thursday" << endl;
            break;
        case 5:
            cout << "Friday" << endl;
            break;
        Default:
            cout << "Weekend" << endl;
            break;
    }

    return 0;
}

Interpretation:

switch (day): The switch statement checks the value of the variable day
Each of the case defines a possible value that day can be taken from 1 to 5.
If day==3, the program will print Wednesday and then exit the switch block because of the use of the break statement.
The default block catches any value that doesn't match the specified cases.

If-else vs Switch-case

If-else is more flexible since it allows more complex conditions and expressions whereas switch-case is mostly more efficient easier and simple to read when there are many (multiple) conditions to evaluate.

Fall-through behavior

In C, C++, and several other programming languages, if a break statement is missing, the execution will continue to the next case which we can see in an example below.

Example with Fall-through:

int day = 2;
switch (day) {
    case 1:
        cout << "Monday";
    case 2:
        cout << "Tuesday"; // This will execute
    case 3:
        cout << "Wednesday"; // This will also execute because there's no break
    default:
        cout << "Unknown day";
}

Switch-Case in JavaScript

In JavaScript, the structure of Switch-case works similarly to that of Python which we can see from the example given below.

Example in JavaScript:

let day = 3;

switch (day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    Case 3:
        console.log("Wednesday");
        break;
    default:
        console.log("Weekend");
}

From the above, Wednesday is printed as day ==3. The default block acts as feedback for other values that aren't handled by the cases.

In summary, the switch case which we have looked into examples are simple alternative to using multiple if-else statements when working with a single expression or variable that has many values.

Explain what the following code does

Based on the given code by the professor which is an algorithm that is written in pseudocode using a switchcase structure, I will be explaining what the code does in detail by breaking everything bit by bit.

Variables:

From the code we have the following;

op, n, a are integers.
exit is known as a Boolean flag, that is set to False.
a is used to store the sum of numbers that are entered.

Program Logic:

The program runs in a cycle (loop) until exist is set to True.
User is prompted to select one of the following given options:
Sum numbers
Show results`
End program`
Based on the user's input (op), one of the following actions takes place:

Case 1: Summing Numbers

User is asked how many numbers they want to sum.
For each of the numbers, the user is prompted to enter a value, which is added to the accumulator variable `a.
After all numbers have been entered, the program then informs the user that the process is completed and waits for the user to press a key.

Case 2: Show Results

The program displays the current sum (a and waits for the user to press a key.

Case 3: End Program

The program clears the screen and prints "Bye =)" and then sets exit to True, which then breaks the cycle (loop) and ends the program.

Default Case:

If the user enters an invalid option, the program notifies them and asks them to press a key to continue.

Key Features

The cycle (loop) repeats until the user selects the option to end the program in case 3
The sum is persistent across different inputs, which means the sum is cumulative unless the program restarts afresh.

Write a program in pseudo-code that asks the user for a number greater than 10 (Do-While), then add all the numbers with an accumulator (While) Example: The user enters 15. The program adds up to 1+2+3+4+5+6+7+8+9+10+11+12+13+14+15.

Here is a program in pseudocode that asks the user for a number greater than 10 (Do-While), then adds all the numbers with an accumulator (While) example.

Algorithm SumNumbers
    Define number, sum, and i As Integer

    // Step 1: Ask for a number greater than 10
    Do
        Print "Enter a number greater than 10: "
        Read number
    While number <= 10

    // Step 2: Initialize sum and counter
    sum = 0
    i = 1

    // Step 3: Add all numbers from 1 to the entered number
    While i <= number Do
        sum = sum + i
        i = i + 1
    EndWhile

    // Step 4: Output the result
    Print "The sum of all numbers from 1 to ", number, " is: ", sum
EndAlgorithm

However, after writing the program several times, I kept getting errors while trying to run the program which at first was what I then wrote in Python.

# Online IDE - Code Editor, Compiler, Interpreter

print('Welcome to @josepha!! Happy Coding :)')
# Function to ask for a number greater than 10
def get_number():
    number = 0
    # Do-While equivalent in Python (using a while loop)
    while number <= 10:
        number = int(input("Enter a number greater than 10: "))
    return number

# Function to calculate the sum from 1 to the entered number
def sum_numbers(number):
    sum = 0
    i = 1
    # While loop to accumulate the sum
    while i <= number:
        sum += i
        i += 1
    return sum

# Main program
number = get_number()
result = sum_numbers(number)

print(f"The sum of all numbers from 1 to {number} is: {result}")

Interpretation:

The get_number() function is the function that keeps asking the user for a number greater than 10 using a while loop. The loop breaks only when a valid number that is greater than 10 is entered.
The sum_numbers(number) function is the function that uses a loop to add all numbers from 1 to the entered number. This function accumulates the result in the sum variable.
The Main program is known as the get_number() function that is used to get a valid input and then calls sum_number,(number) to calculate the sum and show the result.