题解 | #牛群的编号重排#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* reorderCows(ListNode* head) {
        // write code here
        auto head1 = new ListNode(-1);
        auto head2 = new ListNode(-1);
        auto h1end = head1;
        auto h2end = head2;
        ListNode*  pre = nullptr;
        int count = 0;
        while(head!=nullptr){
            count ++;
            if(count % 2 == 0){
                h2end->next = head;
                h2end = h2end->next;
            }
            else{
                h1end->next = head;
                h1end = h1end->next;
            }
            auto n_node = head->next;
            head -> next = nullptr;
            head = n_node;
        }
        h1end->next = head2->next;
        return head1->next;
    }
};