【代码随想录】链表

python 复制代码

		#判断头节点是否空，
		#并且头节点为要删除的值，头节点向后移
        while head and head.val==val:
            head=head.next
        if not head: return
        cur=head
        #当前指针指向的下一个元素为val,当前指针指向下一个的下一个
        #否则，当前指针向后移动一位
        while cur.next:
            if cur.next.val==val:
                cur.next=cur.next.next
            else:
                cur=cur.next
        return head

css 复制代码

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

class MyLinkedList(object):

    def __init__(self):
        self.size=0
        self.head=ListNode(0)


    def get(self, index):
        """
        :type index: int
        :rtype: int
        """
        if index<0 or index>=self.size:
            return -1
        cur=self.head
        for i in range(index+1):
            cur=cur.next
        return cur.val


    def addAtHead(self, val):
        """
        :type val: int
        :rtype: None
        """
        #这个是实现从头部节点加入数据的代码部分
        # p=ListNode(val)
        # p.next=self.head.next
        # self.head.next=p
        # self.size+=1
		
		#这个是调用类内已经写好的addAtIndex函数
        self.addAtIndex(0,val)


    def addAtTail(self, val):
        """
        :type val: int
        :rtype: None
        """
        #这个是实现从尾部节点加入数据的代码部分
        # cur=self.head
        # p=ListNode(val)
        # p.next=None
        # for i in range(self.size):
        #     cur=cur.next

        # cur.next=p
        # self.size+=1
        
        #这个是调用类内已经写好的addAtIndex函数
        self.addAtIndex(self.size,val)

    def addAtIndex(self, index, val):
        """
        :type index: int
        :type val: int
        :rtype: None
        """
        if index<0 or index>self.size:
            return -1
        cur=self.head
        for i in range(index):
            cur=cur.next
        p=ListNode(val)
        p.next=cur.next
        cur.next=p
        self.size+=1



    def deleteAtIndex(self, index):
        """
        :type index: int
        :rtype: None
        """
        if index<0 or index>=self.size:
            return -1
        
        cur=self.head
        for i in range(index):
            cur=cur.next
        cur.next=cur.next.next
        self.size-=1

python 复制代码

        pre=None
        cur=head
        if cur==None: return head
        tmp=cur.next
        while tmp:
            cur.next=pre
            pre=cur
            cur=tmp
            tmp=tmp.next
        cur.next=pre
        return cur

python 复制代码

 		pre=None
        cur=head
        while cur:
            tmp=cur.next
            cur.next=pre
            pre=cur
            cur=tmp
   
        return pre

python 复制代码

  		dummy_head = ListNode(next = head)
        pre=dummy_head
        if dummy_head.next==None: return head
        cur=pre.next
        beh=cur.next
        while beh:
            tmp=beh.next
            pre.next=beh
            beh.next=cur
            cur.next=tmp

            pre=cur
            cur=tmp
            if tmp!=None:
                beh=tmp.next
            else:
                beh=None

        
        return dummy_head.next

python 复制代码

 		dummy=ListNode(next=head)
        slow=dummy
        fast=dummy
        for i in range(n):
            fast=fast.next
        while fast.next:
            fast=fast.next
            slow=slow.next
        slow.next=slow.next.next
        return dummy.next

python 复制代码

		p1,p2=headA,headB
        Asize,Bsize=0,0
        while p1:
            p1=p1.next
            Asize+=1
        while p2:
            p2=p2.next
            Bsize+=1
        if Asize-Bsize>=0:
            p1,p2=headB,headA
            Asize,Bsize=Bsize,Asize
        else:
            p1,p2=headA,headB
        for _ in range(Bsize-Asize):
            p2=p2.next
        while p1:
            if p1==p2:
                return p1
            p1=p1.next
            p2=p2.next
        return None

python 复制代码

		fast,slow=head,head
        while fast and fast.next:
            fast=fast.next.next
            slow=slow.next
            if slow==fast:
                x1=head
                x2=slow
                while x1!=x2:
                    x1=x1.next
                    x2=x2.next
                return x1

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