86. Partition List(分割链表)--M

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.

要求：给定一个链表和n，将链表中值大于n的节点往前排，其余节点相对位置不变。

/**
* 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 **current = &head,**search = &head;
while((*search)!=NULL){
if((*search)->val < x){
if(current==search) {
current = &((*current)->next);
search = &((*search)->next);
}
else{
ListNode *tmp = *search;
*search = tmp->next;
tmp->next = *current;
*current = tmp;
current = &(tmp->next);
}
}
else search = &((*search)->next);
}
return head;
}
};