詳細介紹python資料結構之鍊錶

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資料結構是電腦科學必須掌握的一門學問，之前很多的教材都是用C語言實現鍊錶，因為c有指針，可以很方便的控制內存，很方便就實現鍊錶，其他的語言，則沒那麼方便，有很多都是用模擬鍊錶，不過這次，我不是用模擬鍊錶來實現，因為python是動態語言，可以直接把物件賦值給新的變數。

好了，在說我用python實作前，先簡單說說鍊錶吧。在我們儲存一大波資料時，我們很多時候是使用數組，但是當我們執行插入操作的時候就是非常麻煩，看下面的例子，有一堆資料1,2,3,5,6,7我們要在3和5之間插入4,如果用數組，我們會怎麼做？當然是將5之後的資料往後退一位，然後再插入4,這樣非常麻煩，但是如果用鍊錶，我就直接在3和5之間插入4就行，聽著就很方便。

那麼鍊錶的結構是怎麼樣的呢？顧名思義，鍊錶當然像鎖鏈一樣，由一節節節點連在一起，組成一條資料鏈。

鍊錶的節點的結構如下：

data為自訂的數據，next為下一個節點的位址。

鍊錶的結構為，head保存首位節點的位址：

#接下來我們來用python實作鍊錶

python實作鍊錶

首先，定義節點類別Node：

#

class Node:
  '''
  data: 节点保存的数据
  _next: 保存下一个节点对象
  '''
  def __init__(self, data, pnext=None):
    self.data = data
    self._next = pnext

  def __repr__(self):
    '''
    用来定义Node的字符输出，
    print为输出data
    '''
    return str(self.data)

然後，定義鍊錶類別：

鍊錶要包含：

屬性：

鍊錶頭：head

鍊錶長度：length

方法：

判斷是否為空: isEmpty( )

def isEmpty(self):
  return (self.length == 0

增加一個節點(在鍊錶尾新增):append()

def append(self, dataOrNode):
  item = None
  if isinstance(dataOrNode, Node):
    item = dataOrNode
  else:
    item = Node(dataOrNode)

  if not self.head:
    self.head = item
    self.length += 1

  else:
    node = self.head
    while node._next:
      node = node._next
    node._next = item
    self.length += 1

刪除一個節點: delete()

#删除一个节点之后记得要把链表长度减一
def delete(self, index):
  if self.isEmpty():
    print "this chain table is empty."
    return

  if index < 0 or index >= self.length:
    print &#39;error: out of index&#39;
    return
  #要注意删除第一个节点的情况
  #如果有空的头节点就不用这样
  #但是我不喜欢弄头节点
  if index == 0:
    self.head = self.head._next
    self.length -= 1
    return

  #prev为保存前导节点
  #node为保存当前节点
  #当j与index相等时就
  #相当于找到要删除的节点
  j = 0
  node = self.head
  prev = self.head
  while node._next and j < index:
    prev = node
    node = node._next
    j += 1

  if j == index:
    prev._next = node._next
    self.length -= 1

修改一個節點: update()

def update(self, index, data):
  if self.isEmpty() or index < 0 or index >= self.length:
    print &#39;error: out of index&#39;
    return
  j = 0
  node = self.head
  while node._next and j < index:
    node = node._next
    j += 1

  if j == index:
    node.data = data

尋找一個節點: getItem()

def getItem(self, index):
  if self.isEmpty() or index < 0 or index >= self.length:
    print "error: out of index"
    return
  j = 0
  node = self.head
  while node._next and j < index:
    node = node._next
    j += 1

  return node.data

找出一個節點的索引: getIndex()

def getIndex(self, data):
  j = 0
  if self.isEmpty():
    print "this chain table is empty"
    return
  node = self.head
  while node:
    if node.data == data:
      return j
    node = node._next
    j += 1

  if j == self.length:
    print "%s not found" % str(data)
    return

插入一個節點: insert()

def insert(self, index, dataOrNode):
  if self.isEmpty():
    print "this chain tabale is empty"
    return

  if index < 0 or index >= self.length:
    print "error: out of index"
    return

  item = None
  if isinstance(dataOrNode, Node):
    item = dataOrNode
  else:
    item = Node(dataOrNode)

  if index == 0:
    item._next = self.head
    self.head = item
    self.length += 1
    return

  j = 0
  node = self.head
  prev = self.head
  while node._next and j < index:
    prev = node
    node = node._next
    j += 1

  if j == index:
    item._next = node
    prev._next = item
    self.length += 1

清除鍊錶: clear()

#

def clear(self):
  self.head = None
  self.length = 0

以上就是鍊錶類別的要實作的方法。

執行的結果：

#接下來是完整程式碼：

# -*- coding:utf8 -*-
#/usr/bin/env python

class Node(object):
 def __init__(self, data, pnext = None):
  self.data = data
  self._next = pnext

 def __repr__(self):
  return str(self.data)

class ChainTable(object):
 def __init__(self):
  self.head = None
  self.length = 0

 def isEmpty(self):
  return (self.length == 0)

 def append(self, dataOrNode):
  item = None
  if isinstance(dataOrNode, Node):
   item = dataOrNode
  else:
   item = Node(dataOrNode)

  if not self.head:
   self.head = item
   self.length += 1

  else:
   node = self.head
   while node._next:
    node = node._next
   node._next = item
   self.length += 1

 def delete(self, index):
  if self.isEmpty():
   print "this chain table is empty."
   return

  if index < 0 or index >= self.length:
   print &#39;error: out of index&#39;
   return

  if index == 0:
   self.head = self.head._next
   self.length -= 1
   return

  j = 0
  node = self.head
  prev = self.head
  while node._next and j < index:
   prev = node
   node = node._next
   j += 1

  if j == index:
   prev._next = node._next
   self.length -= 1

 def insert(self, index, dataOrNode):
  if self.isEmpty():
   print "this chain tabale is empty"
   return

  if index < 0 or index >= self.length:
   print "error: out of index"
   return

  item = None
  if isinstance(dataOrNode, Node):
   item = dataOrNode
  else:
   item = Node(dataOrNode)

  if index == 0:
   item._next = self.head
   self.head = item
   self.length += 1
   return

  j = 0
  node = self.head
  prev = self.head
  while node._next and j < index:
   prev = node
   node = node._next
   j += 1

  if j == index:
   item._next = node
   prev._next = item
   self.length += 1

 def update(self, index, data):
  if self.isEmpty() or index < 0 or index >= self.length:
   print &#39;error: out of index&#39;
   return
  j = 0
  node = self.head
  while node._next and j < index:
   node = node._next
   j += 1

  if j == index:
   node.data = data

 def getItem(self, index):
  if self.isEmpty() or index < 0 or index >= self.length:
   print "error: out of index"
   return
  j = 0
  node = self.head
  while node._next and j < index:
   node = node._next
   j += 1

  return node.data


 def getIndex(self, data):
  j = 0
  if self.isEmpty():
   print "this chain table is empty"
   return
  node = self.head
  while node:
   if node.data == data:
    return j
   node = node._next
   j += 1

  if j == self.length:
   print "%s not found" % str(data)
   return

 def clear(self):
  self.head = None
  self.length = 0

 def __repr__(self):
  if self.isEmpty():
   return "empty chain table"
  node = self.head
  nlist = &#39;&#39;
  while node:
   nlist += str(node.data) + &#39; &#39;
   node = node._next
  return nlist

 def __getitem__(self, ind):
  if self.isEmpty() or ind < 0 or ind >= self.length:
   print "error: out of index"
   return
  return self.getItem(ind)

 def __setitem__(self, ind, val):
  if self.isEmpty() or ind < 0 or ind >= self.length:
   print "error: out of index"
   return
  self.update(ind, val)

 def __len__(self):
  return self.length

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