[leetcode][list][sort] 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) {
if(NULL == head || NULL == head->next) return head;
ListNode *p = head->next;//用于遍历原链表
head->next = NULL;//head是新链表的第一个也是最后一个节点，记得next置NULL
while(p){
ListNode *pNext = p->next;//先暂存p的后继节点
ListNode *pCur = head;//用于遍历新链表
ListNode *pre = NULL;//当前节点的前驱
while(pCur && pCur->val < p->val) {//查找p的插入位置
pre = pCur;
pCur = pCur->next;
}
if(NULL == pre){//成为新链表的第一个节点
p->next = head;
head = p;
}
else{//插入位置是pre和pCur之间
pre->next = p;
p->next = pCur;
}
p = pNext;//更新遍历指针
}
return head;
}
};

/**
* 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) {
if (NULL == head || NULL == head->next) return head;
ListNode *p = head->next, *tail = head;//taile指向新链表的最后一个节点
while (p != NULL){
ListNode *pNext = p->next;
if (p->val < head->val){//比最小的小
p->next = head;
head = p;
}
else if (tail->val <= p->val){//比最大的大
tail->next = p;
tail = p;
}
else{//在中间
ListNode *q = head->next, *pre = head;
while (q->val < p->val){
pre = q;
q = q->next;
}
pre->next = p;
p->next = q;
}
p = pNext;
}
tail->next = NULL;
return head;
}
};