题解 | #牛群分隔#分成俩链表，一个储存小于x的值，一个储存大于等于x的值

/**
 * 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
     * @param x int整型
     * @return ListNode类
     */
    ListNode* cow_partition(ListNode* head, int x) {
        // write code here
        ListNode* temp1 = new ListNode(0);
        ListNode* head1 = temp1;
        ListNode* temp3 = new ListNode(0);
        ListNode* head3 = temp3;
        if (head == NULL || head->next == NULL) return head;
        while (head) {
            if (head->val < x) {
                ListNode* temp2 = new ListNode(0);//创建一个接受小于x的值的链表
                temp2->val = head->val;
                temp1->next = temp2;
                temp1 = temp2;
            } else {
                ListNode* temp2 = new ListNode(0);//接收大于等于x的值的链表
                temp2->val = head->val;
                temp3->next = temp2;
                temp3 = temp2;
            }
            head = head->next;
        }
        temp1->next=head3->next;//合并链表
        head3->next==NULL;
        return head1->next;
    }
};