insertionSortList.cpp

// https://leetcode.com/problems/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 *p = head->next, *pstart = new ListNode(0), *pend = head;
            pstart->next = head; //为了操作方便，添加一个头结点
            while(p != NULL) {
                ListNode *tmp = pstart->next, *pre = pstart;
                while(tmp != p && p->val >= tmp->val) {
                    tmp = tmp->next; pre = pre->next;
                }
                if(tmp == p)
                    pend = p;
                else {
                    pend->next = p->next;
                    p->next = tmp;
                    pre->next = p;
                }
                p = pend->next;
            }
            head = pstart->next;
            delete pstart;
            return head;
        }
};