# coding = utf-8

# 双向链表
class Node:

    # 双向链表存在两个指标，一个向前，一个向后
    def __init__(self, new_data):
        self.data = new_data
        self.prev = None
        self.next = None

    def get_data(self):
        return self.data

    def set_data(self, new_data):
        self.data = new_data

    def get_next(self):
        return self.next

    def set_next(self, new_next):
        self.next = new_next

    def get_prev(self):
        return self.prev

    def set_prev(self, new_prev):
        self.prev = new_prev

class DoubleList:

    def __init__(self):
        self.head = None

    # 作头插入时，需要要注意插入顺序，
    # 总之。要注意不要丢失next和prev。
    def add(self, item):
        node = Node(item)
        if not self.is_empty():
            # 待插入节点的后继区指向原头节点
            node.set_next(self.head)
            # 原头节点的前驱区指向待插入节点
            self.head.set_prev(node)
        # 将head指向node
        self.head = node

    # 作尾插入时，需要先判断是否为空列表。因为空列表时，没有next。
    # 为空列表时，尾插入和头插入代码相同。
    # 当不为空时，需要循环到底，再作插入处理
    def append(self, item):
        node = Node(item)
        if self.is_empty():
            # 将head指向node
            self.head = node
        else:
            # 移动到链表尾部
            current = self.head
            while current.get_next() is not None:
                current = current.get_next()
            # 将尾节点cur的next指向node
            current.set_next(node)
            # 将node的prev指向cur
            node.set_prev(current)

    # 指定位置插入节点
    def insert(self, pos, item):
        # 相当于头插入
        if pos <= 0:
            self.add(item)
        # 相当于尾插入
        elif pos >= self.size():
            self.append(item)
        else:
            node = Node(item)
            count = 0
            current = self.head
            # 先将游标指到要插入位置
            while count < pos - 1:
                count += 1
                current = current.get_next()
            # 将node的prev指向cur
            node.set_prev(current)
            # 将node的next指向cur的下一个节点
            node.set_next(current.get_next())
            # 将cur的下一个节点的prev指向node
            current.get_next().set_prev(node)
            # 将cur的next指向node
            current.set_next(node)

    # 删除指定节点数据
    def remove(self, item):
        # 删除时，不需要再使用一个prev变量了。因为双向链表本身有这个指针
        current = self.head
        while current is not None:
            if current.get_data() == item:
                # 在找到节点之后，需要判断是否为首节点
                if current == self.head:
                    self.head = current.get_next()
                    # 判断链表是否只有一个结点
                    if current.get_next():
                        current.get_next().set_prev(None)
                else:
                    current.get_prev().set_next(current.get_next())
                    # 如果存在下一个结点，则设置下一个结点
                    if current.get_next():
                        current.get_next().set_prev(current.get_prev())
                break
            else:
                current = current.get_next()

    # 查找指定数据是否存在
    def search(self, item):
        current = self.head
        found = False
        while current is not None:
            if current.get_data() == item:
                found = True
            current = current.get_next()
        return found

    def is_empty(self):
        return self.head is None

    def __len__(self):
        return self.size()

    def size(self):
        count = 0
        current = self.head
        while current is not None:
            count += 1
            current = current.get_next()
        return count

    def show(self):
        current = self.head
        while current is not None:
            print(current.get_data(), end=' ')
            current = current.get_next()
        print('\n')

if __name__ == '__main__':
    d_list = DoubleList()
    print(d_list.is_empty())
    d_list.add(5)
    d_list.add(4)
    d_list.add(76)
    d_list.add(23)
    d_list.show()
    d_list.append(48)
    d_list.show()
    d_list.append(234)
    d_list.show()
    d_list.insert(2, 100)
    d_list.show()
    d_list.remove(5)
    d_list.show()
    print(d_list.search(48))

C:\Users\Sahara\.virtualenvs\test\Scripts\python.exe C:/Users/Sahara/PycharmProjects/test/python_search.py
True

True

Process finished with exit code