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

.

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *partition(ListNode *head, int x) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if (head == NULL) {
return head;
}
ListNode* less = head;
ListNode* more = head;
ListNode* node = head;
if (node->val >= x) {
while (node && node->val >= x) {
more = node;
node = node->next;
}
if (node) {
less = node;
more->next = less->next;
less->next = head;
head = less;
node = more->next;
}
} else {
while (node && node->val < x) {
less = node;
node = node->next;
}
more = node;
if (more) {
node = more->next;
}
}

while (node) {
if (node->val >= x) {
node = node->next;
more = more->next;

} else {
more->next = node->next;
node->next = less->next;
less->next = node;
less = node;
node = more->next;
}
}
return head;
}
};