抽象數據結構list

• python內置實現了list;但list是一種通用數據結構，類似于c++中的vector
• 下面使用鏈表來實現list;python內置list使用數組（array.Array模塊）來實現

list的數據結構和操作方法如下：

一、實現（基于鏈表）

由于實現方式不同，該實現方式的各種操作時間復雜度不同于內置list

• 方法1：內置list(基于數組實現)
• 方法2：基于鏈表

1.1 無序list

class Node():"""鏈表中的節點，包括數據域和指針域；使用單鏈表實現"""def __init__(self, data):self.data = dataself.next = Nonedef get_data(self):return self.datadef set_next(self, next_node):#python內變量為引用類型，可視作指針self.next = next_nodedef get_next(self):return self.nextclass UnOrderedList():"""無序列表的實現"""def __init__(self):"""構造函數創建一個空list空的單鏈表等價于頭部為空；根據頭部可以遍歷出所有所有鏈表信息故list只存儲頭部節點即可"""#頭部節點初始為Noneself.head = Nonedef add(self, item):"""在鏈表head添加元素"""temp_node = Node(item)temp_node.set_next(self.head)self.head = temp_nodedef isEmpty(self):return self.head == Nonedef size(self):#排除特殊情況count = 0node = self.headwhile node != None:count += 1node = node.get_next()return countdef search(self, item):found = Falsecurrent = self.headwhile current != None and not found:if current.get_data() == item:#found相當于指示器，相當于breakfound = Trueelse:current = current.get_next()return founddef remove(self, item):"""1、找到則刪除，未找到不做任何操作2、刪除節點關鍵是定位相鄰節點；左節點可以用previous表示，右節點用current.get_next()表示3、所以兩個變量previous與current至關重要4、刪除頭結點要分類討論"""found = Falsecurrent = self.headprevious = Nonewhile current != None and not found:if current.get_data() == item:#found相當于指示器，相當于breakfound = True#previous為None:刪除頭結點if previous == None:self.head = current.get_next()else:previous.set_next(current.get_next())else:previous = currentcurrent = current.get_next()def append(self, item):"""追加操作，鏈表首都append需要分類討論"""current = self.headif current == None:self.head = Node(item)else:current = self.head#尋找鏈表最后一個元素while current.get_next() is not None:current = current.get_next() current.set_next(Node(item))def insert(self, pos, item):"""插入操作，鏈表首都append需要分類討論"""if pos == 0:inserted_node = Node(item)inserted_node.set_next(self.head)self.head = inserted_nodeelif 0 < pos <=self.size() :#找到pos位置對應的當前元素current與前置元素previouscurrent = self.headprevious = Nonecount = 0while count < pos:previous = currentcurrent = current.get_next()count += 1inserted_node = Node(item)inserted_node.set_next(current)previous.set_next(inserted_node)def index(self, item):myindex = 0current = self.headif self.size():#非空執行操作，空list不做任何操作count = 0while current.get_data() != item:count += 1current = current.get_next()return countdef pop(self, pos=None):"""pop操作，鏈表首都pop需要分類討論"""#對于缺省值的處理if pos is None:pos = self.size() - 1 if pos == 0:self.head = self.head.get_next()return self.headelif 0 < pos < self.size():current = self.headprevious = Nonecount = 0while count != pos:previous = currentcurrent = current.get_next()count += 1previous.set_next(current.get_next())return currentif __name__ == '__main__':mylist = UnOrderedList()mylist.add(31)mylist.add(77)mylist.add(17)mylist.add(93)mylist.add(26)mylist.add(54)print(mylist.size())print(mylist.search(93))print(mylist.search(100))mylist.add(100)print(mylist.search(100))print(mylist.size())print('*'*50)mylist.remove(54)print(mylist.size())mylist.remove(93)print(mylist.size())mylist.remove(31)print(mylist.size())mylist.remove(11)print(mylist.size())print(mylist.search(93))print(mylist.append(66))print(mylist.size())print(mylist.pop(0))print(mylist.pop())print(mylist.index(17))print(mylist.insert(0, 333))print(mylist.insert(1, 444))print(mylist.index(333))print(mylist.index(444))

用單向鏈表實現的list各操作復雜度為：

• append O(n)
• pop O(n)
• pop(k) O(k)
• add O(1)
• isEmpty O(1)
• size O(n)
• index O(n)
• insert(k) O(k)
• remove O(n)

對比使用數組實現的內置list,有一定性能差距

1.2 有序list

數據結構相同，部分操作方法要做對應修改

class Node():"""鏈表中的節點，包括數據域和指針域；使用單鏈表實現"""def __init__(self, data):self.data = dataself.next = Nonedef get_data(self):return self.datadef set_next(self, next_node):#python內變量為引用類型，可視作指針self.next = next_nodedef get_next(self):return self.nextclass OrderedList():"""有序列表"""def __init__(self):self.head = Nonedef isEmpty(self):return self.head == Nonedef size(self):#排除特殊情況count = 0node = self.headwhile node != None:count += 1node = node.get_next()return countdef remove(self, item):"""1、找到則刪除，未找到不做任何操作2、刪除節點關鍵是定位相鄰節點；左節點可以用previous表示，右節點用current.get_next()表示3、所以兩個變量previous與current至關重要4、刪除頭結點要分類討論"""found = Falsecurrent = self.headprevious = Nonewhile current != None and not found:if current.get_data() == item:#found相當于指示器，相當于breakfound = True#previous為None:刪除頭結點if previous == None:self.head = current.get_next()else:previous.set_next(current.get_next())else:previous = currentcurrent = current.get_next()def search(self, item):current = self.head#trigger1found = False #trigger2stop = False#current is not None既表示當前列表非空，也是判斷條件：遍歷到了list末尾；雙關while current is not None and not found and not stop:if item == current.get_data():#找到目標值，觸發trigger1,退出循環found = Trueelse:if item < current.get_data():#由于list順序排列，一旦當前考察值大于目標值，觸發trigger2,退出循環stop = Falseelse: #自增項;只有當前值小于目標值才自增current = current.get_next()return founddef add(self, item):#1、找到合適位置，記錄在current、previous中current = self.headprevious = Nonestop = Falsewhile current is not None and not stop:if current.get_data() > item:stop = Trueelse:#只有trigger:stop未觸發情況下才自增previous = currentcurrent = current.get_next()temp_node = Node(item)if current == self.head:temp_node.set_next(current)self.head = temp_nodeelse:temp_node.set_next(current)previous.set_next(temp_node)if __name__ == '__main__':mylist = OrderedList()mylist.add(31)mylist.add(77)mylist.add(17)mylist.add(93)mylist.add(26)mylist.add(54)print(mylist.size())print(mylist.search(93))print(mylist.search(100))

二、參考鏈接

http://interactivepython.org/runestone/static/pythonds/BasicDS/ImplementinganOrderedList.html

總結

以上是生活随笔為你收集整理的列表的实现与应用的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。