Linked list - reverse linked list

subject ：

Given the head node of a single linked list pHead, The length is n, After reversing the linked list , Return the header of the new linked list .

For example, when entering a linked list {1,2,3} when ,
After reversal , The original linked list becomes {3,2,1}, So the corresponding output is {3,2,1}.
The above conversion process is shown in the figure below ：

Their thinking ：

Reversing the linked list is to make each node next The pointer points back to the previous node , So here's what we can think about , The steps are as follows ：

among ：

• pre It is used to point to the previous node that the inversion needs to point to , At the beginning pre by nullptr.
• cur It is used to point to the current node .
• next Is used to point to cur Next node of , because cur The node of next If once pointed pre node , So originally cur The next node of will not be found , So we need to use next Point to cur Next node of

Solution code ：

/*
struct ListNode {
	int val;
	struct ListNode *next;
	ListNode(int x) :
			val(x), next(NULL) {
	}
};*/
class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
        ListNode* cur=pHead,*pre=nullptr,*nex=nullptr;
        // Final cur Point to nullptr,pre Point to the last node , That is, reverse the head node of the linked list 
        while(cur){
            nex=cur->next;
            cur->next=pre;
            pre=cur;
            cur=nex;
        }
        return pre;
    }
};