Data structure and algorithm-linked list inversion lead node

1. Enter the head node of a linked list, reverse the list, and return the head node of the inverted list.
The linked table node is defined as follows:    
struct ListNode
{
      int        M_nkey;
      listnode* m_pnext;
};
analysis: This is a widely circulated Microsoft face test. Since this problem can be a good response to the programmer's thinking is tight, after Microsoft has been a lot of companies in the interview with this problem.

int Reversesinglylistnode (ListNode *list) {    listnode  *newlist;    The head node of the new linked list    lnode       *p,*q;       Point to the first node of List, that is, the node p=list to be removed    ;        Null if parameter is empty or memory allocation fails    (p = = NULL | | (NewList = (ListNode *) malloc (sizeof (lnode))) = = null)    {        return null;    }                           Initialize newlist    newlist->next = NULL;                                The first node of the list is placed in turn at the first node of the newlist while    (p->next! = NULL)    {                q = p->next;                           Newlist->next = p->next;       Head Insertion Method        p=newlist->next;        p=q;    }                                The original head node should be released and the pointer to the new head node should be free    (p);    return newlist;}

The second method is to place the node after the first node behind the list each time, which is the original single-linked list.

In order to reverse the single-linked list, we first make the next field of the head node point to Node 2, then the next field of node 1 points to Node 3, and finally the next field of node 2 points to Node 1, the first Exchange is completed, the order becomes the header-Node 2-Node 1-node 3-node 4-null, Then do the same exchange to move the node 3 to the front of Node 2, and then the node 4 moved to the front of the node 3 to complete the reversal, the idea has, it should write code:

int  reversesinglylinkedlist (ListNode *list) {    lnode   *p = NULL;    Lnode   *q = NULL;               if (list = = null) return null;    p = list->next;    while (p->next! = NULL)    {        q = p->next;        P->next = q->next;        Q->next = list->next;        List->next = q;    }    return list;}

Data structure and algorithm-linked list inversion lead node