java 两个有序链表的归并

Posted 2021-05-08

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class MergeTowLists {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {      
        ListNode p = l1, q = l2;
        ListNode dummy = new ListNode(-1);
        ListNode r = dummy;
        while(p!=null || q!=null) {
            if(p == null) {
                r.next = q;
                break;
            } else if(q == null) {
                r.next = p;
                break;
            } else if(p.val < q.val) {
                r.next = p;
                p = p.next;
                r = r.next;
            } else {
                r.next = q;
                q = q.next;
                r = r.next;
            }
        }
        return dummy.next;
    }
}