algorithms-python/algorithms/compression/rle_compression.py at master · Mu-L/algorithms-python · GitHub

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"""

Run-length encoding (RLE) is a simple compression algorithm

that gets a stream of data as the input and returns a

sequence of counts of consecutive data values in a row.

When decompressed the data will be fully recovered as RLE

is a lossless data compression.

"""

def encode_rle(input):

"""

Gets a stream of data and compresses it

under a Run-Length Encoding.

:param input: The data to be encoded.

:return: The encoded string.

"""

if not input: return ''

encoded_str = ''

prev_ch = ''

count = 1

for ch in input:

# Check If the subsequent character does not match

if ch != prev_ch:

# Add the count and character

if prev_ch:

encoded_str += str(count) + prev_ch

# Reset the count and set the character

count = 1

prev_ch = ch

else:

# Otherwise increment the counter

count += 1

else:

return encoded_str + (str(count) + prev_ch)

def decode_rle(input):

"""

Gets a stream of data and decompresses it

under a Run-Length Decoding.

:param input: The data to be decoded.

:return: The decoded string.

"""

decode_str = ''

count = ''

for ch in input:

# If not numerical

if not ch.isdigit():

# Expand it for the decoding

decode_str += ch * int(count)

count = ''

else:

# Add it in the counter

count += ch

return decode_str

algorithms-python/algorithms/compression/rle_compression.py at master · Mu-L/algorithms-python · GitHub

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