题解

list_node * merge_list(list_node * head1, list_node * head2)
{
    //////在下面完成代码
    list_node* res= new list_node();
    list_node* cur= res;
    while(head1 != nullptr && head2 != nullptr) {
        if(head1->val < head2->val) {
            list_node* tmp= new list_node();
            tmp->val = head1->val;
            tmp->next =nullptr;
            cur->next = tmp;
            cur = tmp;
            head1 = head1->next;
        } else if(head1->val >= head2->val) {
            list_node* tmp= new list_node();
            tmp->val = head2->val;
            tmp->next =nullptr;
            cur->next = tmp;
            cur = tmp;
            head2 = head2->next;
        }
    }
    if(head1 != nullptr) cur->next = head1;
    if(head2 != nullptr) cur->next = head2;
    return res->next;
}