哈夫曼樹構造
阿新 • • 發佈:2019-01-09
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Fri Jul 27 18:08:26 2018
@author: luogan
"""
# 樹節點類構建
class TreeNode(object):
def __init__(self, data):
self.val = data[0]
self.priority = data[1]
self.leftChild = None
self.rightChild = None
self.code = ""
# 建立樹節點佇列函式
def creatnodeQ(codes):
q = []
for code in codes:
q.append(TreeNode(code))
return q
# 為佇列新增節點元素,並保證優先度從大到小排列
def addQ(queue, nodeNew):
if len(queue) == 0:
return [nodeNew]
for i in range(len(queue)):
if queue[i].priority >= nodeNew.priority:
return queue[:i] + [nodeNew] + queue[i:]
return queue + [nodeNew]
# 節點佇列類定義
class nodeQeuen(object):
def __init__(self, code):
self.que = creatnodeQ(code)
self.size = len(self.que)
def addNode(self,node):
self.que = addQ(self.que, node)
self.size += 1
def popNode(self):
self.size -= 1
return self.que.pop(0)
# 各個字元在字串中出現的次數,即計算優先度
def freChar(string):
d ={}
for c in string:
if not c in d:
d[c] = 1
else:
d[c] += 1
return sorted(d.items(),key=lambda x:x[1])
# 建立哈夫曼樹
def creatHuffmanTree(nodeQ):
while nodeQ.size != 1:
node1 = nodeQ.popNode()
node2 = nodeQ.popNode()
r = TreeNode([None, node1.priority+node2.priority])
r.leftChild = node1
r.rightChild = node2
nodeQ.addNode(r)
return nodeQ.popNode()
codeDic1 = {}
codeDic2 = {}
# 由哈夫曼樹得到哈夫曼編碼表
def HuffmanCodeDic(head, x):
global codeDic, codeList
if head:
HuffmanCodeDic(head.leftChild, x+'0')
head.code += x
if head.val:
codeDic2[head.code] = head.val
codeDic1[head.val] = head.code
HuffmanCodeDic(head.rightChild, x+'1')
# 字串編碼
def TransEncode(string):
global codeDic1
transcode = ""
for c in string:
transcode += codeDic1[c]
return transcode
# 字串解碼
def TransDecode(StringCode):
global codeDic2
code = ""
ans = ""
for ch in StringCode:
code += ch
if code in codeDic2:
ans += codeDic2[code]
code = ""
return ans
# 舉例
string = "AAGGDCCCDDDGFBBBFFGGDDDDGGGEFFDDCCCCDDFGAAA"
t = nodeQeuen(freChar(string))
tree = creatHuffmanTree(t)
HuffmanCodeDic(tree, '')
print(codeDic1,codeDic2)
a = TransEncode(string)
print(a)
aa = TransDecode(a)
print(aa)
print(string == aa)