【LeetCode】Insertion Sort List

Sort a linked list using insertion sort.

我自己AC的代码花费的时间比较长，下面是看了博客http://www.cnblogs.com/TenosDoIt/p/3422296.html 之后重新写的

class Solution {
public:
    ListNode *insertionSortList(ListNode *head) {
		if (head == NULL || head->next == NULL) {
			return head;
		}
		
		ListNode *sorted_head = head;
		ListNode *sorted_rear = head;
		ListNode *unsorted = head->next;
		
		while (unsorted) {
			ListNode *cur = unsorted;
			unsorted = unsorted->next;
			
			if (cur->val <= sorted_head->val) {
				cur->next = sorted_head;
				sorted_head = cur;
			} else if (sorted_rear->val <= cur->val) {
				sorted_rear->next = cur;
				sorted_rear = cur;
			} else {
				ListNode *less = sorted_head;
				while (less->next && less->next->val < cur->val) {
					less = less->next;
				}
				cur->next = less->next;
				less->next = cur;
			}
		}
		sorted_rear->next = NULL;
		return sorted_head;
	}
};