Python实现的单向循环链表功能示例

class Node(object):  """节点"""  def __init__(self, item):    self.item = item    self.next = Noneclass SinCycLinkedlist(object):  """单向循环链表"""  def __init__(self):    self._head = None  def is_empty(self):    """判断链表是否为空"""    return self._head == None  def length(self):    """返回链表的长度"""    # 如果链表为空，返回长度0    if self.is_empty():      return 0    count = 1    cur = self._head    while cur.next != self._head:      count += 1      cur = cur.next    return count  def travel(self):    """遍历链表"""    if self.is_empty():      return    cur = self._head    print cur.item,    while cur.next != self._head:      cur = cur.next      print cur.item,    print ""  def add(self, item):    """头部添加节点"""    node = Node(item)    if self.is_empty():      self._head = node      node.next = self._head    else:      #添加的节点指向_head      node.next = self._head      # 移到链表尾部，将尾部节点的next指向node      cur = self._head      while cur.next != self._head:        cur = cur.next      cur.next = node      #_head指向添加node的      self._head = node  def append(self, item):    """尾部添加节点"""    node = Node(item)    if self.is_empty():      self._head = node      node.next = self._head    else:      # 移到链表尾部      cur = self._head      while cur.next != self._head:        cur = cur.next      # 将尾节点指向node      cur.next = node      # 将node指向头节点_head      node.next = self._head  def insert(self, pos, item):    """在指定位置添加节点"""    if pos <= 0:      self.add(item)    elif pos > (self.length()-1):      self.append(item)    else:      node = Node(item)      cur = self._head      count = 0      # 移动到指定位置的前一个位置      while count < (pos-1):        count += 1        cur = cur.next      node.next = cur.next      cur.next = node  def remove(self, item):    """删除一个节点"""    # 若链表为空，则直接返回    if self.is_empty():      return    # 将cur指向头节点    cur = self._head    pre = None    # 若头节点的元素就是要查找的元素item    if cur.item == item:      # 如果链表不止一个节点      if cur.next != self._head:        # 先找到尾节点，将尾节点的next指向第二个节点        while cur.next != self._head:          cur = cur.next        # cur指向了尾节点        cur.next = self._head.next        self._head = self._head.next      else:        # 链表只有一个节点        self._head = None    else:      pre = self._head      # 第一个节点不是要删除的      while cur.next != self._head:        # 找到了要删除的元素        if cur.item == item:          # 删除          pre.next = cur.next          return        else:          pre = cur          cur = cur.next      # cur 指向尾节点      if cur.item == item:        # 尾部删除        pre.next = cur.next  def search(self, item):    """查找节点是否存在"""    if self.is_empty():      return False    cur = self._head    if cur.item == item:      return True    while cur.next != self._head:      cur = cur.next      if cur.item == item:        return True    return Falseif __name__ == "__main__":  ll = SinCycLinkedlist()  ll.add(1)  ll.add(2)  ll.append(3)  ll.insert(2, 4)  ll.insert(4, 5)  ll.insert(0, 6)  print "length:",ll.length()  ll.travel()  print ll.search(3)  print ll.search(7)  ll.remove(1)  print "length:",ll.length()  ll.travel()