合并两个有序链表 迭代和递归

struct Node
{
    int data;
    Node* next;
    Node(int x): data(x), next(NULL){}
};

Node* fun1(Node* l1, Node* l2) {
    Node* head = new Node(-1);
    Node* ret = head;
    while (l1 != NULL && l2 != NULL) {
        if (l1->data < l2->data) {
            head->next = l1;
            l1 = l1->next;
        } else {
            head->next = l2;
            l2 = l2->next;
        }
        head = head->next;
    }
    head->next = l1 == NULL ? l2 : l1;
    return ret->next;
}
Node* fun2{Node* l1, Node* l2) {
    if (l1 == NULL) return l2;
    if (l2 == NULL) return l1;
    if (l1->data > l2->data) {
        l2->next = fun2(l1, l2->next);
        return l2;
    } else {
        l1->next = fun2(l1->next, l2);
        return l1;
    }
}