标签：归并排序 tar cpp merge pre color log https NPU
https://leetcode.com/problems/sort-list/
Sort a linked list in O(n log n) time using constant space complexity.
Example 1:
Input: 4->2->1->3 Output: 1->2->3->4
Example 2:
Input: -1->5->3->4->0 Output: -1->0->3->4->5
代码：
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* sortList(ListNode* head) {
if(!head || !head -> next) return head;
ListNode *fast = head, *slow = head, *pre = head;
while(fast && fast -> next) {
pre = slow;
slow = slow -> next;
fast = fast -> next -> next;
}
pre -> next = NULL;
return mergesort(sortList(head), sortList(slow));
}
ListNode *mergesort(ListNode* l1, ListNode* l2) {
ListNode *dummy = new ListNode(-1);
ListNode *cur = dummy;
while(l1 && l2) {
if(l1 -> val < l2 -> val) {
cur -> next = l1;
l1 = l1 -> next;
} else {
cur -> next = l2;
l2 = l2 -> next;
}
cur = cur -> next;
}
if(l1) cur -> next = l1;
if(l2) cur -> next = l2;
return dummy -> next;
}
};
归并排序 学到了
FHFHFH
标签：归并排序 tar cpp merge pre color log https NPU
原文地址：https://www.cnblogs.com/zlrrrr/p/10337874.html
