mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-24 05:21:09 +00:00
cecf43d648
* Pyupgrade to Python 3.9
* updating DIRECTORY.md
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
89 lines
2.3 KiB
Python
89 lines
2.3 KiB
Python
import sys
|
|
|
|
|
|
class Letter:
|
|
def __init__(self, letter, freq):
|
|
self.letter = letter
|
|
self.freq = freq
|
|
self.bitstring = {}
|
|
|
|
def __repr__(self):
|
|
return f"{self.letter}:{self.freq}"
|
|
|
|
|
|
class TreeNode:
|
|
def __init__(self, freq, left, right):
|
|
self.freq = freq
|
|
self.left = left
|
|
self.right = right
|
|
|
|
|
|
def parse_file(file_path):
|
|
"""
|
|
Read the file and build a dict of all letters and their
|
|
frequencies, then convert the dict into a list of Letters.
|
|
"""
|
|
chars = {}
|
|
with open(file_path) as f:
|
|
while True:
|
|
c = f.read(1)
|
|
if not c:
|
|
break
|
|
chars[c] = chars[c] + 1 if c in chars.keys() else 1
|
|
return sorted((Letter(c, f) for c, f in chars.items()), key=lambda l: l.freq)
|
|
|
|
|
|
def build_tree(letters):
|
|
"""
|
|
Run through the list of Letters and build the min heap
|
|
for the Huffman Tree.
|
|
"""
|
|
while len(letters) > 1:
|
|
left = letters.pop(0)
|
|
right = letters.pop(0)
|
|
total_freq = left.freq + right.freq
|
|
node = TreeNode(total_freq, left, right)
|
|
letters.append(node)
|
|
letters.sort(key=lambda l: l.freq)
|
|
return letters[0]
|
|
|
|
|
|
def traverse_tree(root, bitstring):
|
|
"""
|
|
Recursively traverse the Huffman Tree to set each
|
|
Letter's bitstring dictionary, and return the list of Letters
|
|
"""
|
|
if type(root) is Letter:
|
|
root.bitstring[root.letter] = bitstring
|
|
return [root]
|
|
letters = []
|
|
letters += traverse_tree(root.left, bitstring + "0")
|
|
letters += traverse_tree(root.right, bitstring + "1")
|
|
return letters
|
|
|
|
|
|
def huffman(file_path):
|
|
"""
|
|
Parse the file, build the tree, then run through the file
|
|
again, using the letters dictionary to find and print out the
|
|
bitstring for each letter.
|
|
"""
|
|
letters_list = parse_file(file_path)
|
|
root = build_tree(letters_list)
|
|
letters = {
|
|
k: v for letter in traverse_tree(root, "") for k, v in letter.bitstring.items()
|
|
}
|
|
print(f"Huffman Coding of {file_path}: ")
|
|
with open(file_path) as f:
|
|
while True:
|
|
c = f.read(1)
|
|
if not c:
|
|
break
|
|
print(letters[c], end=" ")
|
|
print()
|
|
|
|
|
|
if __name__ == "__main__":
|
|
# pass the file path to the huffman function
|
|
huffman(sys.argv[1])
|