题解 | #合并两个排序的链表#

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode Merge(ListNode list1, ListNode list2) {
        if (list1 == null) {
            return list2;
        }
        if (list2 == null) {
            return list1;
        }
        ListNode mergedHead;
        if (list1.val <= list2.val) {
            mergedHead = list1;
            list1 = list1.next;
        } else {
            mergedHead = list2;
            list2 = list2.next;
        }
        ListNode cur = mergedHead;
        while ( list1 != null || list2 != null ) {
            if (list1 == null) {
                cur.next = list2;
                return mergedHead;
            }
            if (list2 == null) {
                cur.next = list1;
                return mergedHead;
            }
            if (list1.val <= list2.val ) {
                cur.next = list1;
                cur = list1;
                list1 = list1.next;
            } else {
                cur.next = list2;
                cur = list2;
                list2 = list2.next;
            }
        }
        return mergedHead;
    }
}