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run_length_encoding.py
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48 lines (39 loc) · 1.29 KB
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# https://en.wikipedia.org/wiki/Run-length_encoding
def run_length_encode(text: str) -> list:
"""
Performs Run Length Encoding
>>> run_length_encode("AAAABBBCCDAA")
[('A', 4), ('B', 3), ('C', 2), ('D', 1), ('A', 2)]
>>> run_length_encode("A")
[('A', 1)]
>>> run_length_encode("AA")
[('A', 2)]
>>> run_length_encode("AAADDDDDDFFFCCCAAVVVV")
[('A', 3), ('D', 6), ('F', 3), ('C', 3), ('A', 2), ('V', 4)]
"""
encoded = []
count = 1
for i in range(len(text)):
if i + 1 < len(text) and text[i] == text[i + 1]:
count += 1
else:
encoded.append((text[i], count))
count = 1
return encoded
def run_length_decode(encoded: list) -> str:
"""
Performs Run Length Decoding
>>> run_length_decode([('A', 4), ('B', 3), ('C', 2), ('D', 1), ('A', 2)])
'AAAABBBCCDAA'
>>> run_length_decode([('A', 1)])
'A'
>>> run_length_decode([('A', 2)])
'AA'
>>> run_length_decode([('A', 3), ('D', 6), ('F', 3), ('C', 3), ('A', 2), ('V', 4)])
'AAADDDDDDFFFCCCAAVVVV'
"""
return "".join(char * length for char, length in encoded)
if __name__ == "__main__":
from doctest import testmod
testmod(name="run_length_encode", verbose=True)
testmod(name="run_length_decode", verbose=True)