3 Intermediate Python coding challenges (with solutions)

3 Intermediate Python coding challenges (with solutions)

dev.to - Jan 25

The previous Python coding challenges for beginners seem to be well-received so I decided to create another post for intermediate coding challenges. Have fun solving & don't hesistate to share your feedback or solutions in the comment section :)

1. Caesar Cipher

Background:
Caesar's cipher is a simple encryption technique, in which the plaintext character is replaced by a letter some fixed number of positions down the alphabet.

For example, with a right shift of 3, A would be replaced by D, B would become E, and so on.

Caesar's cipher

Task:
Write a Python program to decode the following secret message: N qtaj uwtlwfrrnsl zxnsl Udymts, given that the key is 5.

Starter code:

ciphertext = "N qtaj uwtlwfrrnsl zxnsl Udymts"

def decrypt(ciphertext, key):
    # complete code here

decrypt(ciphertext, 5)
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Sample solution:

def decrypt(ciphertext, key):
    letters = "abcdefghijklmnopqrstuvwxyz"
    letters_upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

    message = ""

    for char in ciphertext:
        if char in letters:      
            position = letters.find(char)
            new_pos = (position - key) % 26
            new_char = letters[new_pos]
            message += new_char
        elif char in letters_upper:
            position = letters_upper.find(char)
            new_pos = (position - key) % 26
            new_char = letters_upper[new_pos]
            message += new_char
        else:
            message += char
        return message

print(decrypt(cipher, 5))
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2. Simple Mastermind Game

Task:
Write a program that randomly generates a 4 digit number. The user has maximum 10 tries to guess the number.

  • If any of the digit guessed is wrong, print "A" to indicate wrong guess.

  • If the digit is guessed correctly but in the wrong position, print "B".

  • If the digit guessed is both the correct value and position, print "C".

Starter code:

import random

def generate_number():
    # complete code here

def input_guess():
    guess = input("Enter your guess: ")
    return guess

def start_game():
    # complete code here

start_game()
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Sample solution:

import random

def generate_number():
    num = random.randint(1000,9999)
    num = [int(x) for x in str(num)]
    return num

def input_guess():
    guess = input("Enter your guess: ")
    return guess

def start_game():
    tries = 0
    number = generate_number()

    while tries < 10:
        result = ""
        guess = [int(i) for i in input_guess()]

        if len(guess) != 4:
            print("Enter only 4 digit number")
            continue

        if guess == number:
            print("You won with ", tries, " attempts.")
            break

        for element in guess:
            if element in number:
                if guess.index(element) == number.index(element):
                    result+="C"
                else:
                    result+="B"
            else:
                result+="A"
        print(result)
        tries += 1

    else:   
        print("You ran out of attempts. The answer is: " , "".join(map(str, number)))   

start_game()
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3. Roman Numerals & Integer Converter

Background:
The Roman numeral system consists of the following symbols:

Symbol Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1000

Numbers are constructed by combining these symbols. For instance, the number 12 can be represented by XII, since X + I + I = 10 + 1 + 1.

The following list is set of rules for Roman numerals:

  • Zero is not represented.

  • A symbol can be repeated only for three times.

  • Roman numerals are repeated to add value: III is equivalent to 1 +1 +1 = 3. However, only powers of 10 may be repeated in this way. Thus, VV is invalid; 5 + 5 would instead be expressed as X.

  • When a Roman numeral is placed after another Roman numeral of greater value, the result is the sum of the numerals. When a Roman numeral is placed before another Roman numeral of greater value, the result is the difference between the numerals.

  • Only I, X, and C can be used as subtractive numerals as shown:

    • I can be used before V(5) and X(10) to make it IV(4) and XV(9) respectively.
    • X cab be used before L(50) and C(100) to make it XL(40) and XC(90) respectively
    • C can be used before D(500) and M(1000) to make them CD(400) and CM(900) respectively.

Task:
Write a program that allows users to either convert integers to roman numerals, or convert roman numerals to integers.

Starter code:

def roman_to_int(roman):
  # complete code here

def int_to_roman(int):
  # complete code here

print(" ---------- Roman Numberals Conversion ----------")  
print(" > 1 - Convert an integer to a roman numerals,")  
print(" > 2 - Convert a roman numerals to an integer.")  
option = input("Choose an option (1 or 2):")  
# complete code here
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Sample solution:

def roman_to_int(s):
    roman_values = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}

    result = 0

    for i in range(len(s)):
        if i + 1 < len(s) and roman_values[s[i]] < roman_values[s[i + 1]]:
            result -= roman_values[s[i]]
        else:
            result += roman_values[s[i]]

    return result


def int_to_roman(x):
    roman_map = { 1: 'I', 4: 'IV', 5: 'V', 9: 'IX', 10: 'X', 40: 'XL', 50: 'L', 90: 'XC', 100: 'C', 400: 'XD', 500: 'D', 900: 'CM', 1000: 'M'}
    integers = list(roman_map)
    symbols = list(roman_map.values())

    i = 12
    result = ""

    while x != 0:
        if integers[i] <= x:
            result += symbols[i]
            x -= integers[i]
        else:
            i -= 1

    return result


print(" ---------- Roman Numberals Conversion ----------")  
print(" > 1 - Convert an integer to a roman numerals,")  
print(" > 2 - Convert a roman numerals to an integer.")  
option = input("Choose an option (1 or 2):")  

if option == "1":
    num = int(input("Enter an integer: "))
    print(int_to_roman(num))
elif option == "2":
    roman = input("Enter a Roman numeral: ")
    print(roman_to_int(roman))
else:
    print("Invalid input.")
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