Leetcode-21-合并两个有序链表

题目

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题解

题解1

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(-1);
        ListNode p = dummy;
        ListNode p1 = l1;
        ListNode p2 = l2;
        while (p1 != null && p2 != null) {
            if (p1.val < p2.val) {
                p.next = p1;
                p = p.next;
                p1 = p1.next;
            } else {
                p.next = p2;
                p = p.next;
                p2 = p2.next;
            }
        }
        while (p1 != null) {
            p.next = p1;
            p = p.next;
            p1 = p1.next;
        }
        while (p2 != null) {
            p.next = p2;
            p = p.next;
            p2 = p2.next;
        }
        return dummy.next;
    }
}