【Leedcode】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) {
         ListNode dummy(INT_MIN);
         ListNode *cur = head;
         while (cur != nullptr) {
             ListNode *pos = findInsertPos(&dummy, cur->val);
             ListNode *temp = cur->next;
             cur->next = pos->next;
             pos->next = cur;
             cur = temp;
         }
         return dummy.next;
     }
 private:
     ListNode *findInsertPos(ListNode *before_head, int key) {
         ListNode *pre = nullptr, *cur = before_head;
         while (cur != nullptr && cur->val <= key) {
             pre = cur;
             cur = cur->next;
         }
         return pre;
     }
 };