Sort a linked list using insertion sort.
class Solution {
public:
ListNode* insertionSortList(ListNode* head) {
if(head == NULL||head->next == NULL)
return head;
ListNode* newhead = new ListNode(-1);
newhead->next = head;
ListNode* p = head->next;
head->next = NULL;//如果后面插入的结点都在head之前，保证排完序的链表结尾指向NULL
while(p != NULL)
{
ListNode* cur = p; //继续从头开始,扫描指针
p = p->next;
ListNode* pre = newhead;//创建的新的链表
ListNode* node = newhead->next;
while(true)
{
if(cur->val<node->val)
{
pre->next = cur; //插入结点
cur->next = node;
break;
}
else
{
pre = node; //查找下一个结点进行比较
node = node->next;
}
if(node == NULL)
{
pre->next = cur;
cur->next = NULL;
break;
}
}
}
return newhead->next;
}
};
