【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;
    }
};