leetcode-剑指 Offer 24. 反转链表

双指针

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class Solution {
    public ListNode reverseList(ListNode head) {
        if(head.next == null){
            return head;
        }

        ListNode cur = head;
        ListNode pre = null;
        while(cur != null){
            cur.next = pre;
            pre = cur;
        }
    }
}

递归

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class Solution {
    public ListNode reverseList(ListNode head) {
        if(head == null || head.next == null){
            return head;
        }
        ListNode res = reverseList(head.next);
        head.next.next = head;
        head.next = null;
        return res;
    }
}