数据结构--链表

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

    def __repr__(self):
        return self.data


class SingleLinkedList:
    def __init__(self, nodes=None):
        self.head = None
        if nodes is not None:
            node = Node(nodes.pop(0))
            self.head = node
            for elem in nodes:
                node.next = Node(elem)
                node = node.next  # 写成Node(elem)也可以

    def __repr__(self):
        node = self.head
        nodes = []

        while node is not None:
            nodes.append(node.data)
            node = node.next
        nodes.append("None")

        return '->'.join(nodes)

    def __iter__(self):
        cur = self.head
        while cur is not None:
            yield cur
            cur = cur.next

    def add_first(self, node):
        '''头部插入节点'''
        node.next = self.head.next
        self.head = node

    def add_last(self, node):
        '''尾部插入节点'''
        if not self.head:
            self.head = node
            return
        # 迭代器
        for cur_node in self:
            pass
        cur_node.next = node

    def add_after(self, target_node_data, new_node):
        if not self.head:
            raise Exception('LList is empty')

        for cur_node in self:
            if cur_node.data == target_node_data:
                new_node.next = cur_node.next
                cur_node.next = new_node
                return

        raise Exception("Node with data '%s' not found" % target_node_data)

    def add_before(self, target_node_data, new_node):
        if not self.head:
            raise Exception('LList is empty')
        # 利用for循环的执行顺序去实现prev_node
        prev_node = self.head
        for cur_node in self:
            if cur_node.data == target_node_data:
                new_node.next = cur_node
                prev_node.next = new_node
                return
            prev_node = cur_node

        raise Exception("Node with data '%s' not found" % target_node_data)

    def remove_node(self, target_node_data):
        # 边界情况
        if not self.head:
            raise Exception('LList is empty')
        # 删除头节点
        if self.head.data == target_node_data:
            self.head = self.head.next
            return
        # 删除头之外节点
        prev_node = self.head
        for cur_node in self:
            if cur_node.data == target_node_data:
                prev_node.next = cur_node.next
                return
            prev_node = cur_node

        raise Exception("Node with data '%s' not found" % target_node_data)


# 一个一个节点
llist = SingleLinkedList()
fnode = Node("1")
llist.head = fnode
snode = Node("2")
tnode = Node("3")
fnode.next = snode
snode.next = tnode
# 列表转链表

ltllist = SingleLinkedList(['a', 'b', 'c'])
ltllist.add_before('c', Node('cc'))
print(ltllist)