Notes

Hailstone numbers are undeciable and always end with 4 2 1

Vocab

Collatz: The Collatz conjecture is one of the most famous unsolved problems in mathematics. The conjecture asks whether repeating two simple arithmetic operations will eventually transform every positive integer into 1.
Hailstone numbers: The sequence of integers generated by Collatz conjecture are called Hailstone Numbers. Examples: Input : N = 7 Output : Hailstone Numbers: 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1 No.
Iteration: The action or a process of iterating or repeating: such as. : a procedure in which repetition of a sequence of operations yields results successively closer to a desired result.
Undecidable problems: An undecidable problem is one that should give a "yes" or "no" answer, but yet no algorithm exists that can answer correctly on all inputs.
Unsolvable problems: An unsolvable problem is one for which no algorithm can ever be written to find the solution.

Hacks Unit 3 Section 18

def collatz(i):
    list_ = [i]
    while i != 1:
        if i % 2 > 0:
             i =((3 * i) + 1)
             list_.append(i)
        else:
            i = (i / 2)
            list_.append(i)
    return list_

while True:
    try:
        i = int(input('Enter i: '))
        break
    except ValueError:
        print('Invalid selection, try again: ', end='')

l = collatz(i)

print('')
print('Collatz sequence:', l)
print('Number of iterations:', len(l) - 1)

Collatz sequence: [12, 6.0, 3.0, 10.0, 5.0, 16.0, 8.0, 4.0, 2.0, 1.0]
Number of iterations: 9

Hacks for Unit 3 Section 17

Inaficent Way to sort letters

Makes a varible for each Food
Then puts them into a list
On a larger Data Scale this would take longer
This one took 7.6 seconds

def food():
    Food1 = "pizza"
    Food2 = input("Input a food")
    Food3 = input("Input a food")
    foods = (Food1, Food2, Food3)
    for i in foods:
        if i == "pizza":
            print("there is pizza")
    return foods


result = food()
print(result)

there is pizza
('pizza', 'sprite', 'chips')

More efficent way

Only has one varible that list each food
Doesn't need to be put in a list
Works better on a larger scale
Only takes 4.1 seconds

def fast():
    foods = ("pizza", input("Input a food"), input("Input a food"))
    for i in foods:
        if i == "pizza":
            print("there is pizza")
    return foods

result = fast()
print(result)

there is pizza
('pizza', 'sprite', 'chips')