Insertion Sort List.cpp

/**
 * 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* helper = new ListNode(-1);
        helper->next = head;
        auto curr = head;
        while(curr->next)
        {
            if(curr->next->val < curr->val)
            {
                //find insert position
                auto pre = helper;
                while(pre->next->val < curr->next->val)
                    pre = pre->next;
                //remove curr->next;
                auto tmp = curr->next;
                curr->next = curr->next->next;
                //insert tmp
                auto next = pre->next;
                pre->next = tmp;
                tmp->next = next;
            }
            else
                curr = curr->next;
        }
        return helper->next;
    }
};