LeetCode – Refresh – 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) {
if (!head || !head->next) return head;
ListNode *result = new ListNode(0);
ListNode *old = new ListNode(0);
old->next = head;
while (old->next) {
ListNode *tmp = old->next, *runner = result;
old->next = tmp->next;
while (runner) {
if (!runner->next || tmp->val < runner->next->val) {
tmp->next = runner->next;
runner->next = tmp;
break;
}
runner = runner->next;
}
}
return result->next;
}
};