Greetings fellow problem solvers! 🤓
As I am learning programming, I decided to spend more time on my problem-solving skills. Practice is a key aspect of the learning process and a great way to stay motivated.
With this new post series, I would like to share with you some code katas' solution. If you feel like it, don't hesitate to take those challenges on your own and share your solutions.
Algorithm/problem solving is just like a muscle that we must often train in order to improve. Today's problems are beginner-friendly, I will slowly bring harder problems on the table as this series is growing up.
Depending on my mood, I will provide solutions written in JavaScript, Python or C#. I can't wait to have your feedbacks and advices!
Table of Contents
Multiples of 3 & 5
From Codewars
The problem:
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Finish the solution so that it returns the sum of all the multiples of 3 or 5 below the number passed in.
My solution (Python):
def solution(number): # Return 0 if argument is negative if number <= 0: return 0 # Create a list to store multiples multiples_list = [] # Loop from 1 to argument for i in range(1, number): if (i % 3 == 0) or (i % 5 == 0): # Add multiples to the list multiples_list.append(i) # Return the sum return sum(multiples_list) Valid Braces
From Codewars
The problem:
Write a function that takes a string of braces, and determines if the order of the braces is valid. It should return true if the string is valid, and false if it's invalid.
All input strings will be nonempty, and will only consist of parentheses, brackets and curly braces: ()[]{}.
What is considered Valid?
A string of braces is considered valid if all braces are matched with the correct brace.
Example:
"(){}[]" => True "([{}])" => True "(}" => False "[(])" => False "[({})](]" => False My solution (Python):
def validBraces(string): # Return False if arg is not a string if type(string) is not str: return False # Return False if arg's length is not even if len(string) % 2 is not 0: return False # Convert string to list braces_list = list(string) # Create a braces dictionnary braces_dictionnary = { "(": ")", "{": "}", "[": "]" } # Create a list of 'opened' braces opened_braces = [] # Loop through the list generated by the string for brace in braces_list: # It is an opening brace if brace in braces_dictionnary: # Push it at the end of our opened braces list opened_braces.append(brace) # It is a closing brace else: # Check if opened braces list is empty if len(opened_braces) == 0: return False # Check if the last encountered opening brace corresponds if braces_dictionnary[opened_braces[-1]] == brace: # It is the same so we remove it from the opened list opened_braces.pop() # They are different, string is not valid! else: return False # Check if there are still opened braces in the list if len(opened_braces) > 0: return False else: return True Roman Numerals Encoder
From Codewars
The problem:
Create a function taking a positive integer as its parameter and returning a string containing the Roman Numeral representation of that integer.
Modern Roman numerals are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero. In Roman numerals 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC. 2008 is written as 2000=MM, 8=VIII; or MMVIII. 1666 uses each Roman symbol in descending order: MDCLXVI.
Help
Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1,000 Example:
solution(1000) # should return 'M' My solution (Python):
def solution(n): # Check that n is an integer if type(n) is not int: return False # Symbols sorted by index sym_dictionnary = { 0: { 1: 'M' }, 1: { 9: "CM", 5: "D", 4: "CD", 1: "C" }, 2: { 9: "XC", 5: "L", 4: "XL", 1: "X" }, 3: { 9: "IX", 5: "V", 4: "IV", 1: "I" }, } # Create a digit list from n digit_list = list(str(n / 10000))[2:] # We will build the result with this list result_list = [] # Loop through the digit list for i in range(0, len(digit_list)): current_digit = int(digit_list[i]) # Until the current digit reaches 0 while current_digit > 0: # Find the appropriate symbol in the dictionnary and push it to the result list for key in sym_dictionnary[i]: if current_digit - key >= 0: current_digit -= key result_list.append(sym_dictionnary[i][key]) break; # Convert to string and return the result return "".join(result_list) Pascal's Triangle
From Codewars
The problem:
In mathematics, Pascal's triangle is a triangular array of the binomial coefficients expressed with formula
Task
Write a function that, given a depth n, returns n top rows of Pascal's Triangle flattened into a one-dimensional list/array.
Example:
n = 1: [1] n = 2: [1, 1, 1] n = 4: [1, 1, 1, 1, 2, 1, 1, 3, 3, 1] My solution (JavaScript):
function pascalsTriangle(n) { // Helper variable that represents the pyramid as an array of arrays const pyramid = [[1]]; // Result variable that will be returned const result = [1]; // Loop until our pyramid has enough rows for (let i = 1; i < n; i++) { const newRow = []; // Populate every slots in a row for (let j = 0; j <= i; j++){ // The current number is the sum of the number at the current index and current index - 1 from the previous row const currentNum = (pyramid[i-1][j] || 0) + (pyramid[i - 1][j - 1] || 0); newRow[j] = currentNum; result.push(currentNum) } // Append a new populated row at the end of every iteration pyramid.push(newRow); } return result; } Persistent Bugger
From Codewars
The problem:
Write a function, persistence, that takes in a positive parameter num and returns its multiplicative persistence, which is the number of times you must multiply the digits in num until you reach a single digit.
Example:
persistence(39) => 3 # Because 3*9 = 27, 2*7 = 14, 1*4=4 # and 4 has only one digit. persistence(999) => 4 # Because 9*9*9 = 729, 7*2*9 = 126, # 1*2*6 = 12, and finally 1*2 = 2. persistence(4) => 0 # Because 4 is already a one-digit number. My solution (Python):
def persistence(n): # Convert a number to a list of digits digit_list = [int(char) for char in str(n)] # Count every loop iteration count = 0 # Loop until we have 1 digit left while len(digit_list) > 1: # Multiply every digits in the list newNumber = 1 for digit in digit_list: newNumber *= digit # Update count and current number values count += 1 digit_list = [int(char) for char in str(newNumber)] return count 
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