哈夫曼编码python算法实现（代码版）

一、问题：      

        请使用哈夫曼编码方法对给定的字符串，进行编码，以满足发送的编码总长度最小，且方便译码。“AABBCCDDEEABCDDCDBAEEAAA”

二、过程：

import heapq
import collections

class Node:
    def __init__(self, char, freq):
        self.char = char
        self.freq = freq
        self.left = None
        self.right = None

    def __lt__(self, other):
        return self.freq < other.freq

def build_frequency_table(text):
    return collections.Counter(text)

def build_huffman_tree(frequencies):
    priority_queue = [Node(char, freq) for char, freq in frequencies.items()]
    heapq.heapify(priority_queue)

    while len(priority_queue) > 1:
        left = heapq.heappop(priority_queue)
        right = heapq.heappop(priority_queue)
        merged = Node(None, left.freq + right.freq)
        merged.left = left
        merged.right = right
        heapq.heappush(priority_q