题解 | 链表中的节点每k个一组翻转

import java.util.*;

public class Main {
    static class ListNode{
        int val;
        ListNode next;
        ListNode(int val){
            this.val = val;
        }
    }
        // 这里全是输入处理
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
            String str = in.nextLine();
            int k = in.nextInt();
            ListNode head = new ListNode(-1);
            ListNode p = head;
            String[] strArray = str.split(" ");
            for(int i = 0; i < strArray.length - 1; i++){
                p.next = new ListNode(Integer.parseInt(strArray[i]));
                p = p.next;
            }
            head = reverseK(head.next, k);
            printList(head);
        }
    }
        // 输出处理
    private static void printList(ListNode head) {
        while(head != null){
            System.out.print(head.val);
            if(head.next != null){
                System.out.print("-&gt;");
            }
            head = head.next;
        }
    }
        // 核心程序
    private static ListNode reverseK(ListNode head, int k) {
        if(k == 1 || head == null || head.next == null){
            return head;
        }
        ListNode a = head, b = head;
        for(int i = 0; i &lt; k; i++){
            if(b == null){
                return head;
            }
            b = b.next;
        }
        ListNode newHead = reverse(a, b);
        head.next = reverseK(b, k);
        return newHead;
    }

    private static ListNode reverse(ListNode a, ListNode b) {
        ListNode pre = null, cur = a;
        while(cur != b){
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return  pre;
    }
}