头插法创建&原地逆置单链表 【Java】

一、头插法创建&原地逆置单链表

public class RotateList {

    public static void main(String[] args) {
        int [] values = new int[]{1,2,3,4};
        Node head = constructList(values);
        printResult("链表创建后结构： ", head);
        Node newHead = reverseList(head);
        printResult("链表逆置后结构： ", newHead);
    }

    /***
     * 头插法创建链表
     * @param values
     * @return
     */
    public static Node constructList(int [] values){
        Node head = new Node(values[0], null);
        for(int i = 1; i <= values.length -1; i++){
            Node node = new Node(values[i], null);
            node.next = head.next;
            head.next = node;
        }
        return head;
    }

    /***
     * 逆置链表
     * @param head
     * @return
     */
    public static Node reverseList(Node head){
        Node pre = null;
        Node cur = head;
        Node next = cur.next;
        while(next != null){
            cur.next = pre;
            pre = cur;
            cur = next;
            next = cur.next;
        }
        cur.next = pre;
        return cur;
    }

    /***
     * 打印结果
     * @param comment
     * @param head
     */
    public static void printResult(String comment, Node head){
        System.out.print(comment);
        Node cur = head;
        while(cur != null){
            System.out.print(cur.value + "-->");
            cur = cur.next;
        }
        if(cur == null){
            System.out.print("null");
        }
        System.out.println();
    }
}

二、运行结果

链表创建后结构： 1-->4-->3-->2-->null
链表逆置后结构： 2-->3-->4-->1-->null