python數據結構與算法（9）
def insert(self, pos, item): """在指定位置添加節點""" if pos <= 0: self.add(item) elif pos > (self.length()-1): self.append(item) else: node = Node(item) cur = self.__head count = 0 # 移動到指定位置的前?個位置 while count < (pos-1): count += 1 cur = cur.next # 將node的prev指向cur node.prev = cur # 將node的next指向cur的下?個節點 node.next = cur.next # 將cur的下?個節點的prev指向node cur.next.prev = node # 將cur的next指向node cur.next = node
刪除元素
def remove(self, item): """刪除元素""" cur = self.__head while cur != None: # 找到了要刪除的元素 if cur.item == item: # 先判斷此結點是否是頭節點 # 頭節點 if cur == self.__head: self.__head = cur.next # 如果存在下?個結點，則設置下?個結點 if cur.next: # 判斷鏈表是否只有?個結點 cur.next.prev = None else: cur.prev.next = cur.next # 如果存在下?個結點，則設置下?個結點 if cur.next: cur.next.prev = cur.prev break else: cur = cur.next
測試
if __name__ == "__main__": ll = DLinkList() 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(4) ll.remove(1) print "length:",ll.length() ll.travel()
單向循環鏈表
單鏈表的?個變形是單向循環鏈表，鏈表中最後?個節點的next域不再為 None，?是指向鏈表的頭節點。
操作
is_empty() 判斷鏈表是否為空 length() 返回鏈表的?度 travel() 遍歷 add(item) 在頭部添加?個節點 append(item) 在尾部添加?個節點 insert(pos, item) 在指定位置pos添加節點 remove(item) 刪除?個節點 search(item) 查找節點是否存在
實現
class Node(object): """節點""" def __init__(self, item): self.item = item self.next = None
class SinCycLinkedlist(object): """單向循環鏈表""" def __init__(self): self.__head = None
def is_empty(self): """判斷鏈表是否為空""" return self.__head == None
def length(self): """返回鏈表的?度""" # 如果鏈表為空，返回?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): """遍歷鏈表""" 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): """頭部添加節點""" node = Node(item) if self.is_empty(): self.__head = node node.next = self.__head else: #添加的節點指向_head node.next = self.__head # 移到鏈表尾部，將尾部節點的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): """尾部添加節點""" node = Node(item) if self.is_empty(): self.__head = node node.next = self.__head else: # 移到鏈表尾部 cur = self.__head while cur.next != self.__head: cur = cur.next # 將尾節點指向node cur.next = node # 將node指向頭節點_head node.next = self.__head
def insert(self, pos, item): """在指定位置添加節點""" if pos <= 0: self.add(item) elif pos > (self.length()-1): self.append(item) else: node = Node(item) cur = self.__head count = 0 # 移動到指定位置的前?個位置 while count < (pos-1): count += 1 cur = cur.next
node.next = cur.next cur.next = node
def remove(self, item): """刪除?個節點""" # 若鏈表為空，則直接返回 if self.is_empty(): return # 將cur指向頭節點 cur = self.__head pre = None while cur.next != self.__head: if cur.item == item: # 先判斷此結點是否是頭節點 if cur == self.__head: # 頭節點的情況 # 找尾節點 rear = self.__head while rear.next != self.__head: rear = rear.next self.__head = cur.next rear.next = self.__head else: # 中間節點 pre.next = cur.next return else: pre = cur cur = cur.next # 退出循環，cur指向尾節點 if cur.item == item: if cur == self.__head: # 鏈表只有?個節點 self.__head = None else: # pre.next = cur.next pre.next = self.__head
def search(self, item): """查找節點是否存在""" 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 False
if __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()python數據結構與算法（9）