LeetCode OJ Partition List

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

For example,
Given 1->4->3->2->5->2 and x = 3,

return 1->2->2->4->3->5.

class Solution {public:    ListNode *partition(ListNode *head, int x) {        if (head == NULL) {            return head;        }        if (head->next == NULL) {            return head;        }        bool first_less = true;        bool first_greater = true;        ListNode *less_head = NULL;        ListNode *less_tail = NULL;        ListNode *greater_head = NULL;        ListNode *greater_tail = NULL;        ListNode *move = head;        while (move != NULL) {            if (move->val < x) {                if (first_less) {                    first_less = false;                    less_head = new ListNode(move->val);                    less_tail = less_head;                } else {                    ListNode *new_less = new ListNode(move->val);                    less_tail->next = new_less;                    less_tail = less_tail->next;                }            } else {                if (first_greater) {                    first_greater = false;                    greater_head = new ListNode(move->val);                    greater_tail = greater_head;                } else {                    ListNode *new_greater = new ListNode(move->val);                    greater_tail->next = new_greater;                    greater_tail = greater_tail->next;                }            }            move = move->next;        }        move = head;        ListNode *move_new = less_head;        ListNode *del;        while (move_new != NULL) {            move->val = move_new->val;            move = move->next;            del = move_new;            move_new = move_new->next;            delete del;        }        move_new = greater_head;        while (move_new != NULL) {            move->val = move_new->val;            move = move->next;            del = move_new;            move_new = move_new->next;            delete del;        }        return head;    }};