题目描述
输入两个单调递增的链表,输出两个链表合成后的链表,当然我们需要合成后的链表满足单调不减规则。

解答:
1.遍历两个链表,按大小顺序拼接。
public class Q_16 {

public ListNode Merge(ListNode list1, ListNode list2) {
    ListNode head = new ListNode(0);
    ListNode movnode = head;

    while (list1 != null && list2 != null) {
        if (list1.val > list2.val) {
            movnode.next = list2;
            list2 = list2.next;
        } else {
            movnode.next = list1;
            list1 = list1.next;
        }
        movnode = movnode.next;
    }
    if (list1 != null) {
        movnode.next = list1;
    }
    if (list2 != null) {
        movnode.next = list2;
    }
    return head.next;
}

}

2.递归
public class Q_16 {

//递归
public ListNode Merge1(ListNode list1, ListNode list2) {
    if (list1 == null) {
        return list2;
    } else if (list2 == null) {
        return list1;
    }else{
        if(list1.val<list2.val){
            list1.next=Merge1(list1.next, list2);
            return list1;
        }else {
            list2.next=Merge1(list1, list2.next);
            return list2;
        }
    }
}

}