707. 设计链表

最新推荐文章于 2024-08-10 19:20:48 发布

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本文详细介绍了两种实现链表的方法：一种是使用数组，另一种是自定义链表节点。通过这两种方式，我们可以实现链表的基本操作，如获取、添加和删除节点。文章深入探讨了每种方法的具体实现细节，为读者提供了丰富的代码示例。

在这里插入图片描述
因为题目说明不使用内置的库
一、直接使用数组实现

class MyLinkedList(object):

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.lst = []
        

    def get(self, index):
        """
        Get the value of the index-th node in the linked list. If the index is invalid, return -1.
        :type index: int
        :rtype: int
        """
        if index > len(self.lst) - 1 or index < 0:
            return -1
        return self.lst[index]
        
        

    def addAtHead(self, val):
        """
        Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list.
        :type val: int
        :rtype: void
        """
        self.lst.insert(0, val)
        

    def addAtTail(self, val):
        """
        Append a node of value val to the last element of the linked list.
        :type val: int
        :rtype: void
        """
        self.lst.append(val)
        

    def addAtIndex(self, index, val):
        """
        Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted.
        :type index: int
        :type val: int
        :rtype: void
        """
        if index > len(self.lst):
            return 
        elif index == len(self.lst):
            self.lst.append(val)
        else:
            self.lst.insert(index, val)
        

    def deleteAtIndex(self, index):
        """
        Delete the index-th node in the linked list, if the index is valid.
        :type index: int
        :rtype: void
        """
        if index > len(self.lst) - 1 or index < 0:
            return 
        self.lst.pop(index)
        


# Your MyLinkedList object will be instantiated and called as such:
# obj = MyLinkedList()
# param_1 = obj.get(index)
# obj.addAtHead(val)
# obj.addAtTail(val)
# obj.addAtIndex(index,val)
# obj.deleteAtIndex(index)

1.索引就是num【index】里面index的值
2.最后一句可以使用 del self.linkedlist[index]
注意pop后是圆括号而del是方括号。

二、自定义链表节点

class Node(object):

    def __init__(self, val):
        self.val = val
        self.next = None


class MyLinkedList(object):

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.head = None
        self.size = 0

    def get(self, index):
        """
        Get the value of the index-th node in the linked list. If the index is invalid, return -1.
        :type index: int
        :rtype: int
        """
        if index < 0 or index >= self.size:
            return -1

        if self.head is None:
            return -1

        curr = self.head
        for i in range(index):
            curr = curr.next
        return curr.val

    def addAtHead(self, val):
        """
        Add a node of value val before the first element of the linked list.
        After the insertion, the new node will be the first node of the linked list.
        :type val: int
        :rtype: void
        """
        node = Node(val)
        node.next = self.head
        self.head = node

        self.size += 1

    def addAtTail(self, val):
        """
        Append a node of value val to the last element of the linked list.
        :type val: int
        :rtype: void
        """
        curr = self.head
        if curr is None:
            self.head = Node(val)
        else:
            while curr.next is not None:
                curr = curr.next
            curr.next = Node(val)

        self.size += 1

    def addAtIndex(self, index, val):
        """
        Add a node of value val before the index-th node in the linked list.
        If index equals to the length of linked list, the node will be appended to the end of linked list.
        If index is greater than the length, the node will not be inserted.
        :type index: int
        :type val: int
        :rtype: void
        """
        if index < 0 or index > self.size:
            return

        if index == 0:
            self.addAtHead(val)
        else:
            curr = self.head
            for i in range(index - 1):
                curr = curr.next
            node = Node(val)
            node.next = curr.next
            curr.next = node

            self.size += 1

    def deleteAtIndex(self, index):
        """
        Delete the index-th node in the linked list, if the index is valid.
        :type index: int
        :rtype: void
        """
        if index < 0 or index >= self.size:
            return

        curr = self.head
        if index == 0:
            self.head = curr.next
        else:
            for i in range(index - 1):
                curr = curr.next
            curr.next = curr.next.next

        self.size -= 1