题解

vector<list_node*> reverseN(list_node * head1, int K) {
    list_node* pre = nullptr;
    list_node* next = nullptr;
    vector<list_node*> res;
    res.push_back(head1);
    while(K--) {
        next = head1->next;
        head1->next = pre;
        pre = head1;
        head1 = next;
    }
    res.push_back(pre);
    res.push_back(head1);
    return res;
}

list_node * reverse_knode(list_node * head1, int K)
{
    //////在下面完成代码
    list_node* cur = head1;
    int n = 0;
    while(cur != nullptr) { n++; cur = cur->next; }
    n /= K; //逆序n次

    vector<list_node*> p; //p[0]：逆序后的尾节点 p[1]：逆序后的头节点 p[2]:逆序后的下一个节点
    vector<vector<list_node*>> list; //每次逆序的P放入list中
    while(n--) {
        p = reverseN(head1, K); //依次逆序K个节点
        list.push_back(p);    //存入P
        head1 = p[2];    //下一个节点给head1
    }
    //将list中的节点头尾相连
    for(int i=0; i<(int)list.size()-1; i++) {
        list[i][0]->next = list[i+1][1];
    }
    list[(int)list.size()-1][0]->next = head1; //接入剩下的节点
    return list[0][1];
}