1. 为什么进行compaction

kudu中的compaction主要针对磁盘中的DiskRowset进行合并，DiskRowset包含3部分数据：BaseData、RedoLog、UndoLog，对应的有下面3种compaction形式：

• MergeCompaction：仅对BaseData合并
• MinorDeltaCompaction：对RedoLog进行合并
• MajorDeltaCompaction：对UndoLog、BaseData、RedoLog进行合并，删除历史版本数据释放磁盘空间

739. Daily Temperatures

Difficulty: Medium

Given a list of daily temperatures T, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.

For example, given the list of temperatures T = [73, 74, 75, 71, 69, 72, 76, 73], your output should be [1, 1, 4, 2, 1, 1, 0, 0].

Note: The length of temperatures will be in the range [1, 30000]. Each temperature will be an integer in the range [30, 100].

1.Stack

利用栈来消除多余的降序数，例如：1, 3, 5, 7, 4, 3, 8中的4, 3在7之后，所以在后续的遍历中完全无用，通过栈可以跳过这部分数据。

287. Find the Duplicate Number

Difficulty: Medium

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one.

Example 1:

Input: [1,3,4,2,2]
Output: 2

3. Longest Substring Without Repeating Characters

Difficulty: Medium

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3 
Explanation: The answer is "abc", with the length of 3\. 

                
                  
                  

Spark的分区器实现包含两种：HashPartitioner和RangePartitioner。

• HashPartitioner：根据key % 分区数来进行分区，可能导致数据倾斜问题
• RangePartitioner：对数据集中的key进行采样，根据采样结果对数据进行分区，由于采样可以反应key的分布情况，所以RangePartitioner可以在一定程度上避免数据倾斜。

为了实现数据集的随机采样，Spark使用了水塘抽样算法(Reservoir Sampling)，实现了未知数据量大小场景下的随机抽样（无法一次性加载到内存的大数据、流数据）。

1. 随机采样1条数据

Given a non-empty array of integers, return the k most frequent elements.

Example 1:

Input: nums = [1,1,1,2,2,3], k = 2
Output: [1,2]

Example 2:

Input: nums = [1], k = 1

                
                  
                  

Given a string s and a non-empty string p, find all the start indices of p's anagrams in s.

Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than 20,100.

The order of output does not matter.

Example 1:

Input:
s: "cbaebabacd" p: "abc"


                
                  
                  

Implement a trie with insert, search, and startsWith methods.

Example:

Trie trie = new Trie();

trie.insert("apple");
trie.search("apple");   // returns true
trie.search("app");     // returns false

                
                  
                  

You are given a list of non-negative integers, a1, a2, ..., an, and a target, S. Now you have 2 symbols + and -. For each integer, you should choose one from + and - as its new symbol.

Find out how many ways to assign symbols to make sum of integers equal to target S.

Example 1:

Input: nums is [1, 1, 1, 1, 1], S is 3. 
Output: 5
Explanation: 


                
                  
                  

Suppose you have a random list of people standing in a queue. Each person is described by a pair of integers (h, k), where h is the height of the person and k is the number of people in front of this person who have a height greater than or equal to h. Write an algorithm to reconstruct the queue.

Note:
The number of people is less than 1,100.

Example

Input:
[[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]]