| 实现思想/算法描述： 1. 逐行读入权值，并将权值输入每个哈夫曼节点中，再将其送入数组，排序后选出最小的两个节点拿出进行合并，将合并后的节点送入数组，并重新排序，然后以上述步骤循环将最后数组中唯一的节点拿出，也就是所需的哈夫曼树 2. 对于建好的哈夫曼树，只要经过前序遍历，即可读出所需编码，然后将编码倒序排列，新建类Block，用于储存字符和对应权重以及编码，先将字符及权重初始化完毕，按从小到大排列，将编码按长度进行从大到小排列，从而一一对应将编码写入，然后打开文件，将原文读入，进行逐行扫描并遍历Block数组实现所有字符的替换，最后将结果写入编码文件 3. 解码时，同样是对应Block数组，进行循环遍历，将正则表达式匹配的编码译为字符 4. 打印字符时，循环计数即可实现每行定字符数输出 5. 打印哈夫曼树时，对哈夫曼树进行层序遍历，把每一层格式化为字符串，然后逐层输出 python实现代码： import re
#引入正则表达式处理包 #新建哈夫曼树类
class Hafftree:
def __init__(self,weight):
self.leftchild=None
self.rightchild=None
self.parent=None
self.weight=weight
#排序方法，使用的是冒泡排序
def sort(list,start,number):
if list[start]==0:
return
for i in range(1,number-1):
for j in range(start,number-i):
if list[i].weight>list[i+1].weight:
temp=list[i]
list[i]=list[i+1]
list[i+1]=temp
else:
continue
#初始化一个具有20个空间的哈夫曼数组
li=[Hafftree(0)]*20 #定义初始化类，用于生成每个权重对应的哈夫曼节点，并存储在数组中
def init(number,infofile):
global li
weight_pa=re.compile(r"\d+")
file=open(infofile)
allmessage=file.readlines()
for i in range(0,len(allmessage)):
message=allmessage[i]
weight=re.findall(weight_pa,message)[0]
weight=int(weight)
li[i]=Hafftree(weight)
#初始化根节点
firsttree=Hafftree(0) #定义建哈夫曼树的方法，用于从哈夫曼数组中建成一个哈夫曼树并读出到根节点中
def buildtree(list,number):
global firsttree
for i in range(0,number-1):
sort(list,i,number)
newnode=Hafftree(list[i].weight+list[i+1].weight)
newnode.leftchild=list[i]
newnode.rightchild=list[i+1]
list[i+1]=newnode
firsttree=list[number-1]
code=[]
string="" #前序遍历，用于生成哈夫曼编码
def pre_order(root,string):
global code
if root!=None:
if root.leftchild==None and root.rightchild==None:
'''print(string)'''
code.append(string)
return 0
else:
pre_order(root.leftchild,string+"0")
pre_order(root.rightchild,string+"1")
else:
return 0
#Block类用于储存关键字，权重及编码
class Block:
def __init__(self,weight,key):
self.weight=weight
self.key=key
self.code=""
list=[] #该方法用于给文件编码
def Coding(infofile,decodefile,encodefile):
global list
global code
for i in range(0,len(code)):
for j in range(0,len(code)-i-1):
if len(code[j])<len((code[j+1])):
temp=code[j+1]
code[j+1]=code[j]
code[j]=temp
weight_pa = re.compile(r"\d")
key_pa=re.compile(r"\w")
file = open(infofile)
allmessage = file.readlines() #初始化Block数组
for i in range(0, len(allmessage)):
message = allmessage[i]
weight = int(re.findall(weight_pa, message)[0])
key=re.findall(key_pa,message)[0]
list.append(Block(weight,key)) #对数组中节点按照权重进行排列
for i in range(1, len(list) - 1):
for j in range(0, len(list) - i):
if list[j].weight > list[j + 1].weight:
temp = list[j + 1]
list[j + 1] = list[j]
list[j] = temp #将对应编码赋值给Block节点
for i in range(0,len(list)):
list[i].code=code[i]
for i in range(0,len(list)):
'''print(list[i].key+" "+str(list[i].weight)+" "+list[i].code+" ")'''
allmessage=open(decodefile).readlines()
encodefile=open(encodefile,"w")
for i in range(0,len(allmessage)):
message=allmessage[i]
'''print(message)''' #进行循环编码
for j in range(0,len(list)):
if list[j]==None:
return
else:
key=list[j].key
code=list[j].code
pattern=re.compile(key)
message=re.sub(pattern,code,message)
'''print(message)'''
encodefile.write(message)
#进行解码的方法，循环遍历字符串进行解码
def Decode(encodefile,resultfile,list):
encodefile=open(encodefile)
allmessage=encodefile.readlines()
resultfile=open(resultfile,"w")
for i in range(0,len(allmessage)):
message=allmessage[i]
for j in range(0,len(list)):
if list[j]==None:
return
key=list[j].key
code=list[j].code
pattern=re.compile(code)
message=re.sub(pattern,key,message)
resultfile.write(message)
#将哈夫曼树以格式化的形式打印出来，层序遍历
def Printtree(firsttree):
list=[]
list.append(firsttree)
global code
position=0
start=1
end=1
string=""
while position while position string=string+str(list[position].weight)+" "
if list[position].leftchild!=None:
list.append(list[position].leftchild)
end=end+1
if list[position].rightchild!=None:
list.append(list[position].rightchild)
end=end+1
position=position+1
print(string)
string=""
start=end
#以下是测试代码
init(3,"test.txt")
buildtree(li,3)
pre_order(firsttree,string)
Coding("test.txt","test2.txt","test3.txt")
Decode("test3.txt","result.txt",list)
Printtree(firsttree) 顺便附测试结果图： 原文：aaaabbbbbbbcccccccccc 编码后：10101010000000011111111111111111111 打印的树： F:\python3.5.2\python.exe F:/untitled2/Haffman.py
21
10 11
4 7
Process finished with exit code 0 |
