leetcode之反转链表

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Reverse a singly linked list

A linked
list can be reversed either iteratively or recursively. Could you implement both?

struct ListNode* reverseList(struct ListNode* head) {

// 链表为空或者只有头结点
if (!head || !head->next)
return head;
struct ListNode* p1 = head, *p2 = head->next, *p3 = p2;

while (NULL != p2) {

p3 = p2->next;
p2->next = p1;
p1 = p2;
p2 = p3;

}
head->next = NULL;
return (head = p1);
}