DCP29 - AAAABBBCCD

'''
This problem was asked by Amazon.
Run-length encoding is a fast and simple method of encoding strings. The basic idea is to represent repeated successive characters as a single count
and character. For example, the string "AAAABBBCCDAA" would be encoded as "4A3B2C1D2A".
Implement run-length encoding and decoding. You can assume the string to be encoded have no digits and consists solely of alphabetic characters.
You can assume the string to be decoded is valid.
'''
from timeit import default_timer as timer

def solve(message):
    n = len(message)
    letters = list()
    letters.append(message[0])
    counters = list()
    counters.append(1)
    for i in range(1, n):
        if message[i] == letters[len(letters)-1]:
            counters[len(counters)-1] += 1
        else:
            letters.append(message[i])
            counters.append(1)

    # Now, I have to create the returned string based on the 2 lists
    result = ""
    if len(letters) != len(counters):
        print("Error using function 'solve'.")
        return -1000
    for i in range(len(letters)):
        result += (str(counters[i]) + letters[i])
    return result

def prettyPrint(message):
    start = timer()
    result = solve(message)
    end = timer()
    elapsed = 10**6 * (end - start)
    print(message + " ----> " + str(result) + " (" + str(round(elapsed, 2)) + " μs)")


# MAIN FUNCTION
print()
messages = ["AAAAAAAAAKK", "AAAABBBCCDAA", "AAABBBaaabbbAAA", "asdfQWE"]
for message in messages:
    prettyPrint(message)