[LeetCode 206] Reverse Linked List

最新推荐文章于 2024-05-11 15:38:10 发布

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本文详细介绍了反转链表的两种方法：迭代法和递归法。通过两个函数实现，阐述了如何在链表中反转节点，并提供了解决问题的思路和代码示例。

Reverse a singly linked list.

solution:

1. Iteration:

two pointers go through linked list, reverse two neigbour list node.

2. Recursion

public ListNode reverseList(ListNode head) {
        ListNode p1 = head;
        if(head == null || head.next == null) return head;
        ListNode p2 = head.next;
        while(p2!=null){
            ListNode p3 = p2.next;
            p2.next = p1;
            p1 = p2;
            p2 = p3;
        }
        head.next = null;
        return p1;
    }

public ListNode reverseList(ListNode head) {
        if(head == null) return null;
        if(head.next == null) return head;
        ListNode secondElem = head.next;
        head.next = null;
        //reverse everything from the second element on
        ListNode reverseRest = reverseList(secondElem);
        //join the two lists
        secondElem.next = head;
        return reverseRest;
    }