要求：如果鏈表長度為N，時間復雜度要求為O(N),額外的空間復雜度要求為O(1)

public class Problem04_ReverseList {
    
//    單鏈表數據結構
    public static class Node {
        public int value;
        public Node next;
        
        public Node(int data) {
            this.value = data;
        }
    }
    
//    逆序單鏈表函數
    public static Node reverseList(Node head) {
        Node pre 
 
= null;
        Node next = null;
        while (head != null) {
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return pre ;
    }

//    雙鏈表數據結構
    public static class DoubleNode {
        public int value;
        public
 
 DoubleNode next;
        public DoubleNode last;
        
        public DoubleNode(int data) {
            this.value = data;
        }
    }

// 逆序雙鏈表函數
    public static DoubleNode reverseList(DoubleNode head) {
        DoubleNode pre = null;
        DoubleNode next = null;
        
        while (head != null
 
) {
            next = head.next;
            head.next = pre;
            head.last = next;
            pre = head;
            head = next;
        }
        return pre;
    }
    
// 打印單鏈表中的數據
    public static void printLinkedList(Node head) {
        System.out.println("LinkedList: ");
        while (head != null) {
            System.out.println(head.value + " ");
            head = head.next;
        }
        System.out.println();
    }
    
//  打印雙鏈表中的數據
    public static void printDoubleLinkedList(DoubleNode head) {
        System.out.println("DoubleLinkedList: ");
        DoubleNode end = null;
        while (head != null) {
            System.out.println(head.value + " ");
            head = head.next;
        }
        System.out.println(" | ");
        while (end != null){
            System.out.println(end.value + " ");
            end = end.last;            
        }
        System.out.println();
    }
    
    public static void main(String[] args) {
        Node head1 = new Node(1);
        head1.next = new Node(2);
        head1.next.next = new Node(3);
        printLinkedList(head1);
        head1 = reverseList(head1);
        printLinkedList(head1);

        DoubleNode head2 = new DoubleNode(1);
        head2.next = new DoubleNode(2);
        head2.next.last = head2;
        head2.next.next = new DoubleNode(3);
        head2.next.next.last = head2.next;
        head2.next.next.next = new DoubleNode(4);
        head2.next.next.next.last = head2.next.next;
        printDoubleLinkedList(head2);
        printDoubleLinkedList(reverseList(head2));

    }

}

運行結果：

LinkedList: 
1 
2 
3 

LinkedList: 
3 
2 
1 

DoubleLinkedList: 
1 
2 
3 
4 
 | 

DoubleLinkedList: 
4 
3 
2 
1 
 |

反轉單向、雙向鏈表