86. Partition List

题目链接

https://leetcode.com/problems/partition-list/

代码

class Solution {
public:
    ListNode* partition(ListNode* head, int x) {
        ListNode *lt = NULL, *lth = NULL, *gt = NULL, *gth = NULL;

        while (head != NULL) {
            if (head->val < x) {
                if (lt != NULL) {
                    lt->next = head;
                } else {
                    lth = head;
                }
                lt = head;
            } else {
                if (gt != NULL) {
                    gt->next = head;
                } else {
                    gth = head;
                }
                gt = head;
            }
            head = head->next;
        }
        if (lth == NULL) {
            return gth;
        } else {
            lt->next = gth;
            if (gt != NULL) {
                gt->next = NULL;
            }
            return lth;
        }
    }
};