Leetcode#86 Partition List

原题地址

凡是涉及链表的题目，代码越清楚越好。

代码：

ListNode *partition(ListNode *head, int x) {
        ListNode *ltHead = NULL;
        ListNode *ltTail = NULL;
        ListNode *geHead = NULL;
        ListNode *geTail = NULL;
        
        while (head) {
            if (head->val < x) {
                if (!ltHead)
                    ltHead = ltTail = head;
                else {
                    ltTail->next = head;
                    ltTail = ltTail->next;
                }
            }
            else {
                if (!geHead)
                    geHead = geTail = head;
                else {
                    geTail->next = head;
                    geTail = geTail->next;
                }
            }
            head = head->next;
        }
        
        if (ltTail)
            ltTail->next = geHead;
        if (geTail)
            geTail->next = NULL;
            
        return ltHead ? ltHead : geHead;
}