21.合并两个有序链表

LeetCode 算法题解与代码实现

class ListNode {
    int val;
    ListNode next;
    ListNode() {}
    ListNode(int val) { this.val = val; }
    ListNode(int val, ListNode next) { this.val = val; this.next = next; }
}
// @lc code=start
/**
 * Definition for singly-linked list.
 */

class Solution {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        ListNode dummy = new ListNode(-1, null);
        ListNode cur = dummy;
        while (list1 != null && list2 != null) {
            if (list1.val <= list2.val) {
                cur.next = list1;
                cur = cur.next;
                list1 = list1.next;
            }
            else if (list1.val > list2.val) {
                cur.next = list2;
                cur = cur.next;
                list2 = list2.next;
            }
        }

        if (list1 != null) {
            cur.next = list1;
        }
        if (list2 != null) {
            cur.next = list2;
        }

        return dummy.next;
    }
}