partition | 易学教程

How to find all partitions of a list S into k subsets (can be empty)?

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问题 I have a list of unique elements, let's say [1,2], and I want to split it onto k=2 sublists. Now I want to have all possible sublists: [ [ [1,2],[] ], [ [1],[2] ], [ [2],[1] ], [ [],[1,2] ] ] And I want to split onto 1<=k<=n sublists, so for k=1 it will be: [ [1, 2] ] How can I do that with Python 3? UPDATE: my goal is to get all possible partitions of list of N unique numbers, where each partition will have k sublists. I would like to show better example than I have shown upper, I hope I

Why pre-partition will benefit spark job because of reducing shuffling?

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问题 Many tutorials mention that pre-partition of RDD will optimize data shuffling of spark jobs. What I'm confused is that, for my understanding pre-partition will also lead to shuffling, why shuffling in advance here will benefit some operation? Especially spark it self will do the optimization for a set of transformations. For example: If I want to join two dataset country (id, country) and income (id, (income, month, year)), what's the difference between this two kind of operation? (I use

Recursive Quick Sort in java

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问题 This is my quicksort Code. It gives me a wrong answer but i think my partition function is correct. public class Quick_Sort { public static void main(String[] args) { int a[] = {99,88,5,4,3,2,1,0,12,3,7,9,8,3,4,5,7}; quicksort(a, 0, a.length-1); } static int partition(int[] a, int low , int hi) { int pivot = hi; int i =low; int j = hi-1; while(i<j) { if(a[i]<=a[pivot]) { i++; } if(a[i]>a[pivot]) { if((a[i]>a[pivot]) && (a[j]<=a[pivot])) { int temp= a[i]; a[i]=a[j]; a[j]=temp; i++; } if(a[j]>a

Partition of Timestamp column in Dataframes Pyspark

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问题 I have a DataFrame in PSspark in the below format Date Id Name Hours Dno Dname 12/11/2013 1 sam 8 102 It 12/10/2013 2 Ram 7 102 It 11/10/2013 3 Jack 8 103 Accounts 12/11/2013 4 Jim 9 101 Marketing I want to do partition based on dno and save as table in Hive using Parquet format. df.write.saveAsTable( 'default.testing', mode='overwrite', partitionBy='Dno', format='parquet') The query worked fine and created table in Hive with Parquet input. Now I want to do partitioned based on the year and

sorting based partition (like in quick-sort)

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问题 This is an interview question: Given an array with 3 kind of objects white,red,black - one should implement the sorting of the array ,such that it will look: {white}*{black}*{red}*. The interwier said - "you can`t use counting sort".His hint was to think about some quick - sort related technique.So I proposed to use a patition which is like quick - sort partition.He just required to use swap only once for each array`s element.I don`t know how to do it....Any advices ?(I am not sure if it is

spark中map与mapPartitions区别

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在spark中，map与mapPartitions两个函数都是比较常用，这里使用代码来解释一下两者区别 import org . apache . spark . { SparkConf , SparkContext } import scala . collection . mutable . ArrayBuffer object MapAndPartitions { def main ( args : Array [ String ] ) : Unit = { val sc = new SparkContext ( new SparkConf ( ) . setAppName ( "map_mapPartitions_demo" ) . setMaster ( "local" ) ) val arrayRDD = sc . parallelize ( Array ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ) ) //map函数每次处理一个/行数据 arrayRDD . map ( element => { element } ) . foreach ( println ) //mapPartitions每次处理一批数据 //将 arrayRDD分成x批数据进行处理 //elements是其中一批数据 //mapPartitions返回一批数据

HIVE QL: How do I extract info from "show partitions table' and use it in a query?

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问题 When I want to select the last month from a big table I can do this: select * from table where yyyymm=(select max(yyyymm) from table) It takes forever. But hive> show partitions table only takes a second. Would it be possible to manipulate show partitions table into a text_string and do something like: select * from table where yyyymm=(manipulated 'partition_txt') 回答1: I tried doing this in Hive but couldn't, so I did it in Spark 2.1.1. val part = spark.sql("SHOW PARTITIONS db.table") //

Recursive function counting and printing partitions of 1 to n-1

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问题 I am trying write a recursive function(it must be recursive) to print out the partitions and number of partitions for 1 to n-1. For example, 4 combinations that sum to 4: 1 1 1 1 1 1 2 1 3 2 2 I am just having much trouble with the function. This function below doesn't work. Can someone help me please? int partition(int n, int max) { if(n==1||max==1) return(1); int counter = 0; if(n<=max) counter=1; for(int i = 0; n>i; i++){ n=n-1; cout << n << "+"<< i <<"\n"; counter++; partition(n,i); }

Faster way to move file in c++ on linux

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问题 I'm trying to move files on linux by using C++. The Problem is, that the source file and the destination folder can be in different partitions. So I can't simply move the files. Ok. I decided to copy the file and delete the old one. //----- bool copyFile(string source, string destination) { bool retval = false; ifstream srcF (source.c_str(), fstream::binary); ofstream destF (destination.c_str(), fstream::trunc|fstream::binary); if(srcF.is_open() && destF.is_open()){ destF << srcF.rdbuf(); /

How to divide a set of numbers into two sets such that the difference of their sum is minimum

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问题 How to write a Java Program to divide a set of numbers into two sets such that the difference of the sum of their individual numbers, is minimum. For example, I have an array containing integers- [5,4,8,2]. I can divide it into two arrays- [8,2] and [5,4]. Assuming that the given set of numbers, can have a unique solution like in above example, how to write a Java program to achieve the solution. It would be fine even if I am able to find out that minimum possible difference. Let's say my