A group of K inverted linked lists

One 、 recursive

• Ideas ：k_reverse take k Nodes reversed , The rest will be called again k_reverse take k Nodes reversed , Until the number of nodes is not equal to k
• The key is to understand part_reverse After k The node is end start ,head ending , So before k Of nodes head After pointing k Of nodes end（ Reversed ）

struct link
{
    
    int a;
    link* next;
};

link* part_reverse(link *begin, link *end) {
    
    link *pre = end->next;
    while(pre != end) {
    
        link *tmp = begin->next;
        begin->next = pre;
        pre = begin;
        begin = tmp;
    }
    return pre;
}

link* k_reverse(link* head, int k) {
    
    int cnt = 0;
    link * end = head;
    while(end != NULL) {
    
        ++cnt;
        if(cnt == k) break;
        end = end->next;
    }
    if(cnt != k) return head;
    link *tmp = part_reverse(head, end);
    head->next = k_reverse(head->next, k);
    return tmp;
}

Two 、 loop