Shaddyjr

# source: https://www.hackerrank.com/challenges/acm-icpc-team/problem
# video: https://youtu.be/tfHd30CGAWs

def acmTeam(topic):
    # keep track of teams (hashmap/dict)
    teams = {}
    length = len(topic)
    for i in range(length - 1): # O(n)
        curr_bin_string = topic[i] # first team member
        # Take each bit set and use OR operation to create combined topic knowledge team

Shaddyjr

# source: https://www.hackerrank.com/challenges/equality-in-a-array/problem
# video: https://youtu.be/CLIVaqu39wU

def equalizeArray(arr):
    # keep dict of counts
    counts = {}
    # keep highest count item
    highest_count_item = arr[0]
    # loop through list to take counts
    for item in arr: # O(n)

Shaddyjr

# source: https://www.hackerrank.com/challenges/beautiful-triplets/problem
# video: https://youtu.be/fOUWTyxYXUQ

def beautifulTriplets(d, arr):
    # Keep a running count dict
    counts = {}
    total = 0
    # loop through list to get counts
    for val in arr: # O(n)
        if val not in counts:

Shaddyjr

# source: https://www.hackerrank.com/challenges/sherlock-and-valid-string/problem
# video: https://youtu.be/WTwih7Ghvig
def isValid(s):
    count_of_chars = dict()
    
    for char in s:
        if char not in count_of_chars:
            count_of_chars[char] = 0
        count_of_chars[char] += 1
            

Shaddyjr

# source: https://www.hackerrank.com/challenges/abbr/problem
# video: https://youtu.be/4WzCFTmjKu4

def abbreviation(a, b):
    n = len(a)
    m = len(b)

    # init dp_list => O(n * m)
    dp_list = [[False] * (m + 1) for _ in range(n + 1)] # + 1 b/c including empty string
    dp_list[0][0] = True # abbreviation("", "") => True (base case)

Shaddyjr

// source: https://www.hackerrank.com/challenges/coin-change
// video: https://www.youtube.com/watch?v=b34GYbwwrJ8
function getWays(n, c) {
    const store = new Array(n + 1).fill(0);
    store[0] = 1;

    for(const coin of c){
        for(let total = coin; total < store.length; total++){
            const remainder = total - coin;
            store[total] += store[remainder];

Shaddyjr

# source: https://www.hackerrank.com/challenges/lisa-workbook/problem
# video: https://youtu.be/G2_o-FqdCTs

def workbook(n, k, arr):
    count = 0

    current_page = 1 # NOTE: we're indexing starting at 1
    for question_count in arr: # O(n)
        pages_added, remaining_questions = divmod(question_count, k)
        for new_chapter_page in range(1, pages_added + 1): # O(pmodk) => O(100mod1) => O(100) => O(1)

Shaddyjr

# source: https://www.hackerrank.com/challenges/richie-rich/problem
# video: https://youtu.be/fcf4gy5V3L4
def count_mismatches(string_1, string_2):
    """
    Returns count of mismatches between two given strings
    """
    assert len(string_1) == len(string_2)
    count = 0
    for char_1, char_2 in zip(string_1, string_2):
        count += char_1 != char_2

Shaddyjr

# source: https://www.hackerrank.com/challenges/sparse-arrays/problem
# Glitched Failure video: https://youtu.be/n9w7Nuy-FmA

function matchingStrings(strings, queries) {
    const memory = {};
    
    // O(n), where n = number of string
    for(const string of strings) memory[string] = (memory[string] || 0) + 1;

    // O(m), where m = number of queries (the lookup is constant time, O(1))

Shaddyjr

# source: https://www.hackerrank.com/challenges/kaprekar-numbers/problem
# video: https://youtu.be/UoHhr2dwP6g

def is_mod_kap(num):
    '''Returns True if num is a modified kaprekar number'''
    sq_num_str = str(num ** 2)
    mid = len(sq_num_str) // 2  # floor division
    left = sq_num_str[:mid] or 0
    right = sq_num_str[mid:] or 0