LeetCode (Insertion Sort List)

Problem:

Sort a linked list using insertion sort.

Solution:

/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* insertionSortList(ListNode* head) {
if(!head || !head->next) return head;
ListNode l(0), *pre = &l;
ListNode *cur = head, *next;
while(cur){
next = cur->next;
while(pre->next && pre->next->val < cur->val)
pre = pre->next;
cur->next = pre->next;
pre->next = cur;
cur = next;
pre = &l;
}
return l.next;
}
};