牛客网：划分链表

/**
 * @author xienl
 * @description 划分链表
 * @date 2022/7/4
 */

public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        ListNode listNode = new ListNode(1, new ListNode(4, new ListNode(3, new ListNode(2, new ListNode(5, new ListNode(2))))));
        System.out.println(solution.partition(listNode, 3));
    }

    /**
     * 双链表
     * @param head
     * @param x
     * @return
     */
    public ListNode partition (ListNode head, int x) {
        // write code here
        ListNode node1 = new ListNode(0);
        ListNode node2 = new ListNode(0);
        ListNode cur1 = node1;
        ListNode cur2 = node2;
        while (head != null){
            if (head.val < x){
                node1.next = head;
                node1 = node1.next;
            } else {
                node2.next = head;
                node2 = node2.next;
            }
            head = head.next;
        }
        node2.next = null;
        node1.next = cur2.next;
        return cur1.next;
    }
}

class ListNode {
    int val;
    ListNode next = null;

    public ListNode(int val) {
        this.val = val;
    }

    public ListNode(int val, ListNode next) {
        this.val = val;
        this.next = next;
    }
}