题目:
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
int getlength(ListNode *head) {
int n = 0;
while(head) head = head->next,++n;
return n;
}
ListNode* split(ListNode *head,int n) {
ListNode *tmp;
while(--n && head) head = head->next;
if(head == nullptr) return head;
tmp = head->next;
head->next = nullptr;
return tmp;
}
void merge(ListNode *&p,ListNode *left,ListNode *right) {
while(left && right) {
if(left->val < right->val) {
p->next = left;
p = p->next;
left = left->next;
}else {
p->next = right;
p = p->next;
right = right->next;
}
}
while(left) {
p->next = left;
p = p->next;
left = left->next;
}
while(right) {
p->next = right;
p = p->next;
right = right->next;
}
}
ListNode* sortList(ListNode* head) {
int n = getlength(head);
ListNode *left,*right;
ListNode *newhead = new ListNode(-1);
newhead->next = head;
ListNode *pre = newhead,*cur,*p;
for(int sz = 1;sz < n;sz <<= 1) {
cur = newhead->next;
p = newhead;
while(cur) {
left = cur;
right = split(left,sz);
cur = split(right,sz);
merge(p,left,right);
}
}
return newhead->next;
}
};