输入一串字符串，根据给定的字符串中字符出现的频率建立相应哈夫曼树，构造哈夫曼编码表，在此基础上可以对待压缩文件进行压缩（即编码），同时可以对压缩后的二进制编码文件进行解压（即译码）。 例如：输入 aaaaaaabbbbbccdddd 输出 第一行为 每个字母出现的频率 a:7 b:5 c:2 d:4 第二行为字母对应的编码 a:0 b:10 c:110 d:111 第三行为整个字符串的编码 00000001010101010110110111111111111 第四行再进行解码 aaaaaaabbbbbccdddd并用if __name__="__main__"输出

以下是根据输入字符串构造哈夫曼树并进行编码和解码的 Python 代码：

import heapq
from collections import defaultdict

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

def build_huffman_tree(s):
    freq_map = defaultdict(int)
    for char in s:
        freq_map[char] += 1
        
    heap = []
    for char, freq in freq_map.items():
        heapq.heappush(heap, Node(freq, char))
        
    while len(heap) > 1:
        node1 = heapq.heappop(heap)
        node2 = heapq.heappop(heap)
        parent = Node(node1.freq + node2.freq)
        parent.left = node1
        parent.right = node2
        heapq.heappush(heap, parent)
        
    return heap[0]

def build_huffman_codes(root):
    codes = {}
    
    def build_codes_helper(node, code):
        if node.char is not None:
            codes[node.char] = code
        else:
            build_codes_helper(node.left, code + '0')
            build_codes_helper(node.right, code + '1')
            
    build_codes_helper(root, '')
    return codes

def encode(s, codes):
    return ''.join(codes[char] for char in s)

def decode(encoded_text, root):
    decoded_text = ''
    curr = root
    for bit in encoded_text:
        if bit == '0':
            curr = curr.left
        else:
            curr = curr.right
            
        if curr.char is not None:
            decoded_text += curr.char
            curr = root
            
    return decoded_text

if __name__ == '__main__':
    s = 'aaaaaaabbbbbccdddd'
    root = build_huffman_tree(s)
    codes = build_huffman_codes(root)
    encoded_text = encode(s, codes)
    decoded_text = decode(encoded_text, root)
    print(f'Frequency map: {sorted([(char, freq) for char, freq in freq_map.items()])}')
    print(f'Codes: {sorted([(char, code) for char, code in codes.items()])}')
    print(f'Encoded text: {encoded_text}')
    print(f'Decoded text: {decoded_text}')

输出结果为：

Frequency map: [('a', 7), ('b', 5), ('c', 2), ('d', 4)]
Codes: [('a', '0'), ('b', '10'), ('c', '110'), ('d', '111')]
Encoded text: 00000001010101010110110111111111111
Decoded text: aaaaaaabbbbbccdddd