ECNA 2017
Abstract Art
Title description : Find the area union of \(n\) polygons.
solution
is said to have templates.
Craters
Topic description : Given \(n\) circles, find the perimeter of the convex hull.
The solution
finds the tangent points of the common tangents of the two circles, makes the convex hull, and judges whether the two points are on the same circle when calculating the perimeter, and whether it is a superior arc or an inferior arc.
Or split each circle into \(3000\) , make a convex hull, and judge whether the two points are on the same circle when calculating the perimeter.
Time complexity: \(O(n^2)\)
DRM Messages
Topic description :
solutionsimulation
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Game of Throwns
Topic description :
solutionsimulation
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Is-A? Has-A? Who Knowz-A?
Title description : There are \(n\) classes, and classes have two relationships: 1. \(A is B\) , \(A\) is a subclass of \(B\) , which is transitive; 2. \ (A has B\) , the members of \(A\) have \(B\) . Subclasses can inherit members of the superclass. Answer several queries, each asking whether the relationship between the two classes holds.
The solution
runs the DAG once to depress the relationship.
Time complexity: \(O(\frac{n^2}{64})\)
Keeping On Track
Topic description :
solution
runs the tree
Time complexity: \(O(n)\)
A Question of Ingestion
Item description : There are \(n\) portions of food, the weight of each serving is \(w_i\) grams, a person can eat \(m\) grams of food at the beginning, eat according to the serial number, each serving can only be eaten once , every time you eat, \(m\) will become the original \(\frac{2}{3}\) , skip one, then \(m\) remains unchanged, if skip two consecutive , then \(m\) changes back to the initial value. Ask how many grams of food you can eat.
solution
is simple \(dp\)
Time complexity: \(O(2nm)\)
Sheba’s Amoebas
Topic description : Count the number of connected blocks.
solution
\(bfs\)
Time complexity: \(O(nm)\)
Twenty Four, Again
Title description : Calculate the minimum cost solution to make up \(24\) points
Time complexity: \(O(4!\times 3^3 \times 4^2)\)
Workout for a Dumbbell
Topic description :
Solution
simulation.