[LeetCode] Partition List

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) {} * }; */#define LN ListNodeclass Solution {public:    ListNode *partition(ListNode *head, int x) {        // Start typing your C/C++ solution below        // DO NOT write int main() function                LN sguard(-1);    LN hguard(-1);    LN* sTail=&sguard;    LN* hTail=&hguard;    while(head)    {    if (head->val<x)    {    sTail->next=head;    sTail=head;    }    else    {    hTail->next=head;    hTail=head;    }    head=head->next;    }    sTail->next=hguard.next;    hTail->next=NULL;    return sguard.next;    }};