根据电文中各字符出现的频率，建立哈夫曼树，并设计字符的哈夫曼编码。 1) 建立并输出哈夫曼树的存储结构； 2) 根据哈夫曼树，设计并输出对应字符的哈夫曼编码； 3) 将指定接收到的电文进行译码并输出。

好的，以下是实现该任务的 Python 代码：

import heapq
from collections import defaultdict


class HuffmanNode:
    def __init__(self, char=None, freq=0, left=None, right=None):
        self.char = char
        self.freq = freq
        self.left = left
        self.right = right

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


def build_huffman_tree(text):
    freq_dict = defaultdict(int)
    for char in text:
        freq_dict[char] += 1

    heap = [HuffmanNode(char, freq) for char, freq in freq_dict.items()]
    heapq.heapify(heap)

    while len(heap) > 1:
        left = heapq.heappop(heap)
        right = heapq.heappop(heap)
        parent = HuffmanNode(freq=left.freq + right.freq, left=left, right=right)
        heapq.heappush(heap, parent)

    return heap[0]


def build_huffman_codes(node, code='', codes={}):
    if node.char:
        codes[node.char] = code
    else:
        build_huffman_codes(node.left, code + '0', codes)
        build_huffman_codes(node.right, code + '1', codes)
    return codes


def encode_text(text, codes):
    return ''.join(codes[char] for char in text)


def decode_text(encoded_text, node):
    text = ''
    current_node = node
    for bit in encoded_text:
        current_node = current_node.left if bit == '0' else current_node.right
        if current_node.char:
            text += current_node.char
            current_node = node
    return text


if __name__ == '__main__':
    # 例子
    text = 'hello world'
    huffman_tree_root = build_huffman_tree(text)
    huffman_codes = build_huffman_codes(huffman_tree_root)
    encoded_text = encode_text(text, huffman_codes)
    decoded_text = decode_text(encoded_text, huffman_tree_root)

    print('Huffman Tree:')
    print(huffman_tree_root.__dict__)

    print('Huffman Codes:')
    print(huffman_codes)

    print('Encoded Text:')
    print(encoded_text)

    print('Decoded Text:')
    print(decoded_text)

这段代码实现了建立哈夫曼树、设计字符的哈夫曼编码、对指定接收到的电文进行译码功能。你可以根据需求自行修改代码。