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30 September 2023

Developing Algorithms Student Teaching Lesson

by

Lets start off with the basics. What is an algorithm?

What are algorithms used for?

Why are algorithms important?

# Pseudo Code 1
'''

DISPLAY ("What is the temperature outside in F?")
temp <- INPUT()
IF (temp >= 90)
{
    DISPLAY("its too hot outide")
}
ELSE 
{
    IF (temp >= 65){
        DISPLAY ("sure I will play outside")
    }
    ELSE 
    {
        DISPLAY ("its too cold outside")
    }
}

# Psuedo Code 2
DISPLAY ("What is the temperature outside in F?")
temp <- INPUT()
IF (temp >= 90)
{
    DISPLAY("its too hot outide")
}
IF (temp >= 65)
{
        DISPLAY ("sure I will play outside")
}
IF (temp < 65)
{
        DISPLAY ("its too cold outside")
}

'''

What is the difference between the two pieces of code in the cell above?

# Code 1
print("What is the temperature outside in F?")
temp = int(input())

if temp >= 90: 
    print("its too hot outide")
else:  
    if temp >= 65:
        print("sure I will play outside")
    else: 
        print("its too cold outside")
# Code 2
print("What is the temperature outside in F?")
temp = int(input())

if temp >= 90: 
    print("its too hot outide")
if temp >= 65:
    print("sure I will play outside")
if temp < 65:
    print("its too cold outside")
What is the temperature outside in F?
its too hot outide
sure I will play outside

What happens if we plug 56 for the temp? What happens if we plug 95 in?

If we plug 56 in, then it will display the text “its too cold outside.” It first checks the first input, if temp is greater than or equal to 90. Which it isn’t so it moves on to the next if. If temp is greater than or equal to 65, which it isn’t so it checks the last if/else statement and displays the text its too cold outside.

If we plug 95 in we get two different results. Code one displays “its too hot outide” but code two displays “its too hot outide” and “sure I will play outside.” Why is this?

Popcorn Hack #1

Adjust Pseudo Code #2 so that it has the same output as Code #1 for all inputs.

# Insert your code here: 
'''
    
DISPLAY ("What is the temperature outside in F?")
temp <- INPUT()
IF (temp >= 90)
{
    DISPLAY("its too hot outide")
}
ELIF (temp >= 65)
{
        DISPLAY ("sure I will play outside")
}
ELIF (temp < 65)
{
        DISPLAY ("its too cold outside")
}

    '''

Conditionals vs Booleans

Quick reminder:

We have given an algorithm that uses conditionals and two boolean statements that should have the same output as the conditional. Which boolean statement works and which one doesn’t?

Conditional:

# Psuedo Code
IF (isHoliday)
{
    driveWork<- False
}
ELSE
{
    IF (iswWeekday)
    {
        driveWork <_ True
    }
    ELSE
    {
        driveWork <- False
    }
}

Boolean

# Option 1: 
driveWork <- ( (isHoliday) AND (isWeekday))

# Option 2: 
driveWork <- ( (NOT (isHoliday)) AND (isWeekday))

Answer

Option 2 is the correct answer

Popcorn Hack #2

Using the commands listed below, move the robot (gray triangle) through the white squares to the gray square wihtout touching the black squares in the least amount of lines as possible.

Commands allowed:

# Insert your code here: 
'''

if CAN_MOVE() = True:
    MOVE_FORWARD()
else:
    ROTATE_RIGHT()

'''

Optional Popcorn Hack

Change your code to an algorithm that works for any given course.

Hint: use if, elif, else, and CAN_MOVE()

# Insert your code here: 
'''

if CAN_MOVE() = True:
    MOVE_FORWARD()
else:
    rn = numpy.random.uniform(1,2)
    if rn = 1:
        ROTATE_RIGHT()
    else:
        ROTATE_LEFT()

'''

#This should eventually solve any walkable course given enough time.

Combining Selection and/or Iteration

Create an algorithm that uses selection and/or iteration to determine the cost of one item. THe display at the stores says the follorwing:

# Psuedo Code
'''

DISPLAY ("What is the cost of the item?")
cost <- INPUT()
DIPLAY ("Is the tag green or red (type "True" if it is green, type "False" for red)")
tag <- BOOL(INPUT())
IF (tag == True) # Check if it is green tag (refer to lines above)
{
    cost <- 0.75 * cost
}
IF (tag == False) # Check if it is green tag (refer to lines above)
{
    cost <- 0.40 * cost
}
cost <- 1.10 * cost 

'''
print("What is the cost of the item?")
cost = int(input())
print("Is the tag green or red (type "True" if it is green, type "False" for red)")
tag = bool(input())

if tag == True: # Check if it is green tag (refer to lines above)
    cost = 0.75 * cost
if tag == False: # Check if it is green tag (refer to lines above)
    cost = 0.40 * cost
cost = 1.10 * cost # accounting for tax

Famous Collatz Conjecture

  1. Start with any positive integer
  2. IF that number is even, divide by 2
  3. If that number is odd, multiply by 3 and add 1
  4. Repeat steps 2 and 3 until you reach the number 1

6 -> 3 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1

Collatz proposed that this sequence of numbers would always terminate at 1. The problem of whether this is true or not for all positive integers is still unsolved today.

Lets create an algorithm that will start with any positive integer “n” and display the full sequence of numbers that result from this conjecture.

# Pseudo Code 
'''

DISPLAY ("choose a value for n")
n <- INPUT() 
DISPLAY (n)
REPEAT UNTIL (n = 1)
{
    IF (n MOD 2 = 0)
    {
        n <- n/2
    }
    ELSE 
    {
        n <- 3 * n + 1
    }
DISPLAY (n)
}

'''
# Code 
print("choose a value for n")
n = int(input())
print(n)
while n != 1: 
    if n % 2 == 0: 
        n = n/2
    else: 
        n = (n*3)+1
    print(n)
choose a value for n
6
3.0
10.0
5.0
16.0
8.0
4.0
2.0
1.0

Popcorn hack #3

We are given an algorhtim (below) for a robot to move from the current square to the grey square, completing the course (below). However it doesn’t work. Why does the given algorithm not work?

Using the commands listed below, fix the algorithm

Commands allowed: MOVE_FORWARD()

Course:

Given Algorithm

'''

REPEAT UNTIL (goalReached)
{
    IF (CAN_MOVE(FORWARD))
    {
        MOVE_FORWARD
    }
    ELSE
    {
        IF CAN_MOVE(RIGHT)
        {
            ROTATE_RIGHT
            MOVE_FORWARD
        }
    }
}

'''

Put your answer to the question “Why does the given algorithm not work?” here:

# Insert your updated algorithm here: 

#If black squares trigger CAN_MOVE() = False, then this does work. If they don't, then this is a solution:

'''
segments = [3,5,2]
for n in segments:
    while i < n:
        MOVE_FORWARD()
        i += 1
    ROTATE_RIGHT()

'''

#This will run the selected course independent of obstacle positions.

Homework

import numpy as np

score = max(np.random.randint(1,10,4))


#Or if you want the long way
attempts = 0
score = 0
while attempts < 4:
    tempscore = np.random.randint(1,10)
    if tempscore > score:
        score = tempscore
    attempts += 1
7

Use the following flowchart to assist you:

tags: