Answer to interview question from Cassidoo’s newsletter (12/29/25):

puzzle_251229.py

def replaceRepeats(s, n):
    count = 0
    output = ''
    for c in s:
        if c == str(n):
            count += 1
        elif count > 0 and c != str(n):
            output += str(count)
            output += c
            count = 0
        else:
            output += c
    if count > 0:
        output += str(count)
    
    return output

assert replaceRepeats('1234500362000440', 0), '1234523623441'
assert replaceRepeats('000000000000', 0), '12'
assert replaceRepeats('123456789', 1), '123456789'

print('Happy 2026 🥳🎉')