leetcode - 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) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if (head == NULL || head->next == NULL)
            return head;
        ListNode * itr =head->next;
        head->next = NULL;
        while (itr != NULL){
            ListNode * node = head, * last =NULL;
            ListNode *next = itr->next;
            while ((node != NULL) && (node->val < itr->val)){
                last = node;
                node = node->next;
            }
            itr->next = node;
            if (node == head)
                head = itr;
            else
                last->next = itr;
            itr = next;
        }
        return head;
    }
};