有一個(gè)單鏈表，請(qǐng)?jiān)O(shè)計(jì)一個(gè)算法，使得每K個(gè)節(jié)點(diǎn)之間逆序，如果最后不夠K個(gè)節(jié)點(diǎn)一組，則不調(diào)整最后幾個(gè)節(jié)點(diǎn)。例如鏈表1->2->3->4->5->6->7->8->null，K=3這個(gè)例子。調(diào)整后為，3->2->1->6->5->4->7->8->null。因?yàn)镵==3，所以每三個(gè)節(jié)點(diǎn)之間逆序，但其中的7，8不調(diào)整，因?yàn)橹挥袃蓚€(gè)節(jié)點(diǎn)不夠一組。

給定一個(gè)單鏈表的頭指針head,同時(shí)給定K值，返回逆序后的鏈表的頭指針。

/*
   struct ListNode {
   int val;
   struct ListNode *next;
   ListNode(int x) : val(x), next(NULL) {}
   };*/
class KInverse {
    public:
        ListNode* inverse(ListNode* head, int k) {
            // write code here
            int cnt = 1;
            ListNode *first = head, *curr = head, *next_gp = head,
                     *local_curr = head, *pre_end = head, *local_pre=head, *local_nxt = head;
            while(curr){
                if(k == cnt){
                    // 記錄第一段需要反轉(zhuǎn)的段前和段后
                    head = curr;
                    next_gp = curr->next;
                    local_pre = next_gp;
                    // 反轉(zhuǎn)內(nèi)部節(jié)點(diǎn)
                    while(local_curr != next_gp){
                        local_nxt = local_curr->next;
                        local_curr->next = local_pre;
                        local_pre = local_curr;
                        local_curr = local_nxt;
                    }
                    // 為下次做準(zhǔn)備
                    curr = first;
                    first = next_gp;
                    pre_end = curr;
                }else if(cnt > k && 0 == cnt%k){
                    // 記錄段前和段后，并將收尾相連
                    pre_end->next = curr;
                    next_gp = curr->next;
                    local_pre = next_gp;
                    local_curr = first;
                    // 反轉(zhuǎn)內(nèi)部節(jié)點(diǎn)
                    while(local_curr != next_gp){
                        local_nxt = local_curr->next;
                        local_curr->next = local_pre;
                        local_pre = local_curr;
                        local_curr = local_nxt;
                    }
                    // 為下次做準(zhǔn)備
                    curr = first;
                    first = next_gp;
                    pre_end = curr;
                }
                curr = curr->next;
                ++cnt;
            }
            return head;
        }
};