[LeetCode 148] Insertion Sort List

Sort a linked list using insertion sort.

/**
* 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 == nullptr || head->next == nullptr) return head;

ListNode *min = head;
ListNode *max = head;

ListNode *cur = max->next;

while(cur != nullptr)
{
if(min->val >= cur->val)
{
min = cur;
cur = cur->next;

min->next = head;
head = min;
max->next = nullptr;
}

else if(max-> val <= cur -> val)
{
max->next = cur;
cur = cur->next;
max = max->next;
max->next = nullptr;
}

else
{
ListNode *mid = min->next;
ListNode *left = min;
ListNode *p = cur;

while(mid!= nullptr)
{
if(mid->val > cur->val)
{
p = p->next;
left->next = cur;
cur->next = mid;
cur = p;
mid = nullptr; //Stop the loop
}
else if(mid->val <= cur->val)
{
left = mid;
mid = mid->next;
}
}
}
}

return head;
}
};