题目描述
Sort a linked list in O(n log n) time using constant space complexity.
Example1:
Input: 4->2->1->3 Output: 1->2->3->4
Example2:
Input: -1->5->3->4->0 Output: -1->0->3->4->5
Example3:
Input: " 3+5 / 2 " Output: 5
解题思路
- 使用冒泡排序
- 时间复杂度O(n^2)
/**
* 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 == nullptr){
return nullptr;
}
ListNode* cur = head;
while(cur -> next){
ListNode* pnext = cur -> next;
while(pnext != nullptr){
if(cur -> val > pnext -> val){ // 这里其实是 找了一个最小的 放在了cur这里
swap(cur -> val, pnext -> val);
}
pnext = pnext -> next;
}
cur = cur -> next;
}
return head;
}
};
