intersection | 易学教程

Intersection of two nested lists in Python

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I've a problem with the nested lists. I want to compute the lenght of the intersection of two nested lists with the python language. My lists are composed as follows: list1 = [[1,2], [2,3], [3,4]] list2 = [[1,2], [6,7], [4,5]] output_list = [[1,2]] How can i compute the intersection of the two lists? I think there are two reasonable approaches to solving this issue. If you don't have very many items in your top level lists, you can simply check if each sub-list in one of them is present in the other: intersection = [inner_list for inner in list1 if inner_list in list2] The in operator will

Finding the intersection of two 3D polygons

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问题 a.k.a. Polygon clipping algorithm in 3D a.k.a. Finding the collision manifold between 2 colliding polygons Most algorithms for polygon clipping are described in detail for 2D and described as being extendable to 3D but without details. For example the sutherland-hodgman clipping algorithm Having been unable to find any 3D implementations or pseudo code on the internet I am now asking here (and attempting to answer my own question) The algorithm would take two shapes such as those shown below:

Find common elements in 2D numpy arrays

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问题 If I have two (or more) 2D arrays, how can I get only common elements between the arrays given a row number. For example, I have arrays in the format: time, position, velocity, acceleration I want to get the two arrays to only have the same time elements, so row 0. I can use np.intersect1d(array1[:, 0], array2[:, 0]) which gives all the common times, but I want to either extract all matching rows/columns from array1/2 or remove non common time elements. In the end array1 and array2 will have

Date Range Intersection Splitting in SQL

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问题 I have a SQL Server 2005 database which contains a table called Memberships. The table schema is: PersonID int, Surname nvarchar(30), FirstName nvarchar(30), Description nvarchar(100), StartDate datetime, EndDate datetime I'm currently working on a grid feature which shows a break-down of memberships by person. One of the requirements is to split membership rows where there is an intersection of date ranges. The intersection must be bound by the Surname and FirstName, ie splits only occur

Ray-triangle intersetion

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How can I test intersesion ray and triangle, and if it exist how to get distance from ray origin to intersection point?? What optimization I can use, if in my program I've got to check 1 ray to ~10000 triangles ?? A single polygon-ray intersection test is trivial and just involves making sure that the ray crosses at least one side of it (check them individually) or across the plane defined by the triangle between the sides of it. The optimization comes into not checking against polygons that the ray has no chance at all of crossing. Depending on how high of a dimension you're working in, how

Efficient all-pairs set intersection on GPU

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问题 I have n sets, subsets of a finite universe. I want to calculate the n*n matrix in which the (I, J) entry contains the cardinality of the intersection of set I and set J . n is in the order of 50000 . My idea is to split the matrix into blocks sufficiently small so to have one thread per entry. Every thread should calculate the intersection using bitwise and . Are there more efficient approaches to solve this problem? 回答1: I'm going to assume you want to compute it as you described: actually

Looking for a non “brute force” algorithm to remove intersecting areas of a collection of Rects

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问题 I have an n-sized collection of Rects, most of which intersect each other. I'd like to remove the intersections and reduce the intersecting Rects into smaller non-intersecting rects. I could easily brute force a solution, but I'm looking for an efficient algorithm. Here's a visualization: Original: Processed: Ideally the method signature would look like this: public static List<RectF> resolveIntersection(List<RectF> rects); the output would be greater or equal to the input, where the output

Range intersection / union

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I'm developing a programming language for which I want to provide a Range data type which for now is, not as usually, a list of pairs of int values (x,y) with the constraint that x < y . I say not as usually because usually a range is just a pair but in my case it is more than than, allowing to have for example 1 to 5, 7 to 11, 13 to 22 all contained in a single object. I would like to provide two functions to generate the union and the instersection of two ranges, that should contain the least number of non-overlapping intervals from a couple of ranges.. so for example 1 to 5 || 3 to 8 = 1 to

Check if map in C++ contains all the keys from another map

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问题 I am planning to use two maps in C++, of type: std::map<char, Node> , where Node is a custom class. Suppose I have two maps, m1 and m2 of the type above, I want to find out whether m1 contains all keys present in m2 . In other words, I want to verify that the intersection of the set of keys of m1 and m2 is the same as the set of keys of m2 . I could iterate over all keys in m2 and do a find() or count() on m1 , but that would seem like a waste and would probably be slow. I say this because

Patterns for the overlap of two objects

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I'm sure this has already been asked and answered so I apologize in advance for that but I'm not figuring out the correct keywords to search for. Searching for "Pattern" hits way too many Q & A's to be useful. I'm working on a regression testing app. I'm displaying a form on the screen and according to which user is logged in to the app some of the fields should be read-only. So I can abstract a field object and I can abstract a user object but what pattern should I be looking at to describe the intersection of these two concepts? In other words how should I describe that for Field 1 and User