[LeetCode]: 206: Reverse Linked List

题目：

Reverse a singly linked list.

 

思路1：直接用循环遍历即可

 

代码：

    public static ListNode reverseList(ListNode head) {
        if(head == null || head.next == null){
            return head;
        }
        
        ListNode nodeCurrent = head.next;
        ListNode nodeLast= head;
        
        head.next = null;
        
        while(nodeCurrent != null){
            ListNode tempNode = nodeCurrent.next;
            nodeCurrent.next = nodeLast;
            nodeLast = nodeCurrent;
            nodeCurrent = tempNode;
        }
        
        return nodeLast;
    }

 

思路2：递归

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