[LeetCode]Insertion Sort List

/**
* 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) {
// IMPORTANT: Please reset any member data you declared, as
// the same Solution instance will be reused for each test case.
if(head == NULL) return head;
ListNode dummy(-1);
dummy.next = head;
ListNode* prev = head;
ListNode* cur = prev->next;
while(cur)
{
if(cur->val >= prev->val)//greater or equal
{
prev = cur;
cur = cur->next;
}
else//smaller
{
//first find the insert position
ListNode* insertPrev = &dummy;
ListNode* insertCur = dummy.next;
while(insertCur->val < cur->val)
{
insertPrev = insertCur;
insertCur = insertCur->next;
}
//then insert
prev->next = cur->next;
cur->next = insertCur;
insertPrev->next = cur;
cur = prev->next;
}
}
return dummy.next;
}
};