LeetCode - 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 tox.

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) {
if(head==NULL){
return head;
}
ListNode *small=new ListNode(0),*large=new ListNode(0),*p=head,*s=small,*l=large;
while(p){
if(p->val<x){
s->next=p;
s=s->next;
}else{
l->next=p;
l=l->next;
}
p=p->next;
}
l->next=NULL;
s->next=large->next;
head=small->next;
delete small;
small=NULL;
delete large;
large=NULL;
return head;
}
};