链表节点定义:

class ListNode///单链表节点{public:    int val;    ListNode *next;    ListNode(int x): val(x),next(nullptr) {}};struct RandomListNode{
   ///随机链表节点        int label;        RandomListNode *next,*random;        RandomListNode(int x):label(x),next(nullptr),random(nullptr){}};class TreeNode {
   ///树节点表示    public:    int val;    TreeNode *left;    TreeNode *right;    TreeNode(int x): val(x),left(nullptr),right(nullptr){}};

就地逆置

ListNode* revOnPlace(ListNode *head)    {        ListNode dummy(-1);//假的头节点        ListNode *curr = head;        head = &dummy;        while(curr)        {            ListNode *tmp = curr->next;            curr->next = head->next;            head->next = curr;            curr = tmp;        }        return dummy.next;    }