LeetCode 147. 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(0);        while (head != NULL) {            ListNode *pre = &dummy;            ListNode *cur = head;            head = head->next;            while ((pre->next != NULL) && (pre->next->val <= cur->val)) {                pre = pre->next;            }            if (pre->next == NULL) {                pre->next = cur;                cur->next = NULL;            }            else {                cur->next = pre->next;                pre->next = cur;            }        }        return dummy.next;    }};