cartesian-product

问题 I have a binary matrix A of dimension mxn with m>n in Matlab. I want to construct a matrix B of dimension cxn listing row wise each element of the Cartesian product of the row indices of the ones contained in A . To be more clear consider the following example. Example: %m=4; %n=3; A=[1 0 1; 0 0 1; 1 1 0; 0 0 1]; %column 1: "1" are at rows {1,3} %column 2: "1" are at row {3} %column 3: "1" are at rows {1,2,4} %Hence, the Cartesian product {1,3}x{3}x{1,2,4} is %{(1,3,1),(1,3,2),(1,3,4),(3,3,1)

问题 There are two tables that are not related to each other(No foreign keys). How to show them together in MySQL? TABLE1 TABLE2 Result 回答1: You can use this too: SELECT t2.date, t1.name FROM table1 t1 CROSS JOIN table2 t2 回答2: Try This.. SELECT t2.date, t1.name FROM table1 t1, table2 t2 ORDER BY t1.name ASC 回答3: Try simply SELECT t2.date, t1.name FROM table1 t1, table2 t2 回答4: Try this: SELECT DATE, NAME FROM TABLE1, TABLE2 回答5: None of those will work. If you want to learn how to do this

问题 I have a very weird problem which has some constrains that make it difficult to solve. I have a list of lists and I want to do the combinations of all items in those lists. Each item has a name and a value. Here is an example: Main List: List 01: Item 01: name:name01, value:value01 Item 02: name:name02, value:value02 List 02: Item 01: name:name03, value:value03 List 03: Item 01: name:name04, value:value04 Item 02: name:name05, value:value05 The end result should look like this: Some List:

问题 I have a large dataset of string ids, that can fit into memory on a single node in my spark cluster. The issue is that it consumes most of the memory for a single node. These ids are about 30 characters long. For example: ids O2LWk4MAbcrOCWo3IVM0GInelSXfcG HbDckDXCye20kwu0gfeGpLGWnJ2yif o43xSMBUJLOKDxkYEQbAEWk4aPQHkm I am looking to write to file a list of all of the pairs of ids. For example: id1,id2 O2LWk4MAbcrOCWo3IVM0GInelSXfcG,HbDckDXCye20kwu0gfeGpLGWnJ2yif O2LWk4MAbcrOCWo3IVM0GInelSXfcG

问题 This question was severely rewritten as per suggestion from @leftaroundabout. An earlier version may be seen in the edit history. Haskell is famous for the fact that it facilitates thought, allowing more direct encoding of mathematical abstractions. Cartesian product is a very basic mental object many are familiar with since the very childhood. Yet, there is barely a type for it in Haskell. I think I need one, to enable my thinking to flow, if nothing else. (Although this post is actually

问题 I am currently trying to merge three datasets for analysis purposes. I am using certain common fields to establish the connections between the datasets. In order to create the connections I have tried using the following type of query: MATCH (p1:Person),(p2:Person) WHERE p1.email = p2.email AND p1.name = p2.name AND p1 <> p2 CREATE UNIQUE (p1)-[IS]-(p2); Which can be similarly written as: MATCH (p1:Person),(p2:Person {name:p1.name, email:p1.email}) WHERE p1 <> p2 CREATE UNIQUE (p1)-[IS]-(p2);

问题 Need Hints to design an efficient algorithm that takes the following input and spits out the following output. Input: two sorted arrays of integers A and B, each of length n Output: One sorted array that consists of Cartesian product of arrays A and B. For Example: Input: A is 1, 3, 5 B is 4, 8, 10 here n is 3. Output: 4, 8, 10, 12, 20, 24, 30, 40, 50 Here are my attempts at solving this problem. 1) Given that output is n^2, Efficient algorithm can't do any better than O(n^2) time complexity.

问题 I have been searching for weeks on how to come up with piece of code which I could applied the cartesian product. Let's say I have two arrays : int M[2]= {1,2}; int J[3] = {0,1,2}; So the code will takes those two arrays in apply the rule M X J therefore we will have the pairs (1,0)(1,1)(1,2)(2,0)(2,1)(2,2) and I want the new result to be saved into a new array where each index in the array contains a pair , for example c[0] = (1,0). Help please :( 回答1: Here is an simple example of

问题 I have been searching for weeks on how to come up with piece of code which I could applied the cartesian product. Let's say I have two arrays : int M[2]= {1,2}; int J[3] = {0,1,2}; So the code will takes those two arrays in apply the rule M X J therefore we will have the pairs (1,0)(1,1)(1,2)(2,0)(2,1)(2,2) and I want the new result to be saved into a new array where each index in the array contains a pair , for example c[0] = (1,0). Help please :( 回答1: Here is an simple example of

问题 SELECT user_id, SUM(COALESCE(point_points, 0)) AS total_points, SUM( CASE WHEN point_date > '$this_month' THEN point_points ELSE 0 END) AS month_points, COUNT(DISTINCT c_id) AS num_comments, COUNT(DISTINCT rant_id) AS live_submissions FROM users LEFT JOIN points ON users.user_id = points.point_userid LEFT JOIN comments ON ( c_userid = user_id ) LEFT JOIN rants ON ( rant_poster = user_id AND rant_status = 1 ) WHERE user_id = $id GROUP BY user_id Basically live_submissions and num_comments