/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* struct ListNode *next;
* };
*/
struct ListNode* reverseList(struct ListNode* head) {
struct ListNode * current_node,*next_node,ret;
if(head == NULL){
return head;
}
current_node = head->next;
head->next = NULL;
while(current_node != NULL){
next_node = current_node->next;
current_node->next = head;
head = current_node;
current_node = next_node;
}
return head;
}