数据结构是计算机科学必须掌握的一门学问，之前很多的教材都是用C语言实现链表，因为c有指针，可以很方便的控制内存，很方便就实现链表，其他的语言，则没那么方便，有很多都是用模拟链表，不过这次，我不是用模拟链表来实现，因为python是动态语言，可以直接把对象赋值给新的变量。
好了，在说我用python实现前，先简单说说链表吧。在我们存储一大波数据时，我们很多时候是使用数组，但是当我们执行插入操作的时候就是非常麻烦，看下面的例子，有一堆数据1,2,3,5,6,7我们要在3和5之间插入4,如果用数组，我们会怎么做？当然是将5之后的数据往后退一位，然后再插入4,这样非常麻烦，但是如果用链表，我就直接在3和5之间插入4就行，听着就很方便。
那么链表的结构是怎么样的呢？顾名思义，链表当然像锁链一样，由一节节节点连在一起，组成一条数据链。
链表的节点的结构如下：
data为自定义的数据，next为下一个节点的地址。
链表的结构为，head保存首位节点的地址：
接下来我们来用python实现链表
python实现链表
首先，定义节点类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)
然后，定义链表类：
链表要包括：
属性：
链表头：head
链表长度：length
方法：
判断是否为空: isEmpty()
def isEmpty(self): return (self.length == 0
增加一个节点(在链表尾添加): 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
删除一个节点: 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 'error: out of index' 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
修改一个节点: update()
def update(self, index, data): 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 if j == index: node.data = data
查找一个节点: 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
查找一个节点的索引: 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
插入一个节点: 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
清空链表: clear()
def clear(self): self.head = None self.length = 0
以上就是链表类的要实现的方法。
执行的结果：
接下来是完整代码：
# -*- coding:utf8 -*-#/usr/bin/env pythonclass 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 'error: out of index' 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 'error: out of index' 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 = '' while node: nlist += str(node.data) + ' ' 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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