LeetCode--Sort List Question Sort a linked list in O(n log n) time using constant space complexity. Solution 看到对链表的排序,时间复杂度O(n log n),首先想到的就是归并排序. 但是这里其中有两个技巧: 就是将两个链表分开的时候,用到了fast-slow法,这是在处理链表分治,也就是找中间节点的一种有效方法. 还有就是merge的过程,也用到了递归的方式. Code /** * D…

Given a string, sort it in decreasing order based on the frequency of characters. Example 1: Input: "tree" Output: "eert" Explanation: 'e' appears twice while 'r' and 't' both appear once. So 'e' must appear before both 'r' and 't'. Th…

Sort a linked list in O(n log n) time using constant space complexity. 常见排序方法有很多,插入排序,选择排序,堆排序,快速排序,冒泡排序,归并排序,桶排序等等..它们的时间复杂度不尽相同,而这里题目限定了时间必须为O(nlgn),符合要求只有快速排序,归并排序,堆排序,而根据单链表的特点,最适于用归并排序.代码如下: C++ 解法一: class Solution { public: ListNode* sortList(L…

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and bl…

原题地址:https://oj.leetcode.com/problems/sort-colors/ 题意: Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integer…

Sort List Sort a linked list in O(n log n) time using constant space complexity. 使用Merge Sort, 空间复杂度是 O(logN) 因为使用了栈空间. SOLUTION 1: 使用Merge Sort来解决问题. 为什么不用QuickSort? 因为随机访问对于链表而言太耗时,而heap sort不可行. 注意,Find Mid用了2种解法.或者是让Fast提前结束,或是让Fast先走一步,目的就是要取得中间…

Status: AcceptedRuntime: 66 ms 题意:根据给出的单链表,用O(nlogn)的时间复杂度来排序.由时间复杂度想到快排.归并这两种排序.本次用的是归并排序.递归将链表的规模不断二分到只剩下1或2个元素为止,这也是递归出口,一旦出现这两种情况就可以返回.这里有个问题,链表也能二分?可以的,只是麻烦了些,用两个指针可以实现找到中点.本次代码没有详细分析具体的复杂度,但确实是归并. 注意:要考虑空链表,单个元素的链表,以及多个元素的链表. LeetCode的代码: /** *…

Given a sorted array of integers nums and integer values a, b and c. Apply a function of the form f(x) = ax2 + bx + c to each element x in the array. The returned array must be in sorted order. Expected time complexity: O(n) Example: nums = [-4, -2,…

Given a sorted array of integers nums and integer values a, b and c. Apply a function of the form f(x) = ax2 + bx + c to each element x in the array. The returned array must be in sorted order. Expected time complexity: O(n) Example: nums = [-4, -2,…

Sort a linked list in O(n log n) time using constant space complexity. /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode *sort…

Given a string, sort it in decreasing order based on the frequency of characters. Example 1: Input: "tree" Output: "eert" Explanation: 'e' appears twice while 'r' and 't' both appear once. So 'e' must appear before both 'r' and 't'. Th…

Sort a linked list in O(n log n) time using constant space complexity. 分析:题目要求时间复杂度为O(nlogn),所以不能用quickSort(最坏O(n^2)),可以使用mergeSort. 对一个链表进行归并排序,首先注意归并排序的基本思想:找到链表的middle节点,然后递归对前半部分和后半部分分别进行归并排序,最后对两个以排好序的链表进行Merge. 而找到链表中间点可以利用快慢指针的思想:用两个指针,一个每次走两步…

题目: Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, an…

Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index. According to the definition of h-index on Wikipedia: "A scientist has index h if h of his/her N papers have a…

描述: Sort a linked list in O(n log n) time using constant space complexity. 在O(n*log(n))的时间复杂度,常数级空间复杂度内对一个链表进行排序 采用归并排序,用快慢指针将链表分成两部分,最后合并两个链表. /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x…

Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330. Note: The result may be very large, so you need to return a string instead of an i…

Sort a linked list using insertion sort. 利用插入排序对一个链表进行排序 思路和数组中的插入排序一样,不过每次都要从链表头部找一个合适的位置,而不是像数组一样可以从要插入的位置开始从后往前找合适的位置 class Solution(object): def insertionSortList(self, head): dummy = ListNode(-1) dummy.next,cur= head,head while cur and cur.next:…

Sort a linked list in O(n log n) time using constant space complexity. 以时间复杂度O(n log n)排序一个链表. 归并排序,在链表中不需要多余的主存空间 tricks:用快慢指针找到中间位置,划分链表 class Solution(object): def sortList(self, head): if not head or not head.next: return head pre, slow, fast = N…

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and bl…

原题地址:http://oj.leetcode.com/problems/sort-list/ 题意:链表的排序.要求:时间复杂度O(nlogn),空间复杂度O(1). 解题思路:由于题目对时间复杂度和空间复杂度要求比较高,所以查看了各种解法,最好的解法就是归并排序,由于链表在归并操作时并不需要像数组的归并操作那样分配一个临时数组空间,所以这样就是常数空间复杂度了,当然这里不考虑递归所产生的系统调用的栈.   这里涉及到一个链表常用的操作,即快慢指针的技巧.设置slow和fast指针,开始它们都…

Sort ColorsGiven an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, wh…

Given an array with n objects colored red, white or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, whit…

Question Sort a linked list in O(n log n) time using constant space complexity. Solution 分析,时间复杂度要求为nlogn,因此得考虑归并排序,但是空间必须为常量,因此得注意指针的操作. Code /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x)…

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and bl…

Sort a linked list in O(n log n) time using constant space complexity. 这道题目非常简短的一句话.给链表排序,看到nlogn.我们能够来简单复习一下排序. 首先说一下这个nlogn的时间复杂度(依据决策树我们能够得出这个界限).是基于比較排序的最小上限,也就是说.对于没有一定范围情况的数据来说.最快的排序思路就是归并和高速排序了(当然详细的參数系数还是由更详细的设置决定的).对于数组的话,假设使用归并排序,不是in place…

Sort a linked list in O(n log n) time using constant space complexity. Hide Tags Linked List Sort   基于单项链表的排序,时间为nlogn ,O(1)空间,其实及将数组的快速排序用链表实现,并用递归来维护拆分与合并. #include <iostream> using namespace std; /** * Definition for singly-linked list. */ struct…

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and bl…

题意: 一个数组只可能含有3种数据,分别为1,2,3,请将数组排序(只能扫一遍). 思路: 如果扫两遍的话,用个桶记录一下,再赋值上去就行了. class Solution { public: void sortColors(vector<int>& nums) { ]={}; ; i<nums.size(); i++) cnt[nums[i]]++; ,i=; j<; j++) ) nums[i++]=j; } }; AC代码 还有这种傻瓜方法,扫一遍先将2移到末尾,再扫…

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1:Given intervals [1,3],[6,9], insert and merge […

Given a collection of intervals, merge all overlapping intervals. For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,18]. 合并重叠区间 class Solution(object): def merge(self, intervals): """ :type intervals: List[Interval] :rtyp…