LeetCode.206_[链表]_反转链表

1.题目

2.解题思路（一）

建立一个新的头节点，将原先链表上从头到尾的节点依次使用头插法插到新的头节点上

class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode first = new ListNode(0);
        ListNode temp1 = head;
		ListNode temp2 = first;
        while(temp1 != null) {
			ListNode next = temp1.next;
			temp1.next = temp2.next;
			temp2.next = temp1;
			temp1 = next;
		}
        return first.next;
    }
}

3.解题思路（二）

利用栈的先进后出

class Solution {
    public ListNode reverseList(ListNode head) {
        Stack<Integer> stack = new Stack<Integer>();
        ListNode temp1 = head;
		while(temp1 != null) {
			stack.push(temp1.val);
			temp1 = temp1.next;
		}
		ListNode temp2 = head;
		while(!stack.isEmpty()) {
			temp2.val = stack.pop();
			temp2 = temp2.next;
		}
        return head;
    }
}

4.官方的递归解法

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

作者：LeetCode
链接：https://leetcode-cn.com/problems/reverse-linked-list/solution/fan-zhuan-lian-biao-by-leetcode/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

解释来源于leetcode用户