segmenttree | A segment tree implementation in Python | Dataset library
kandi X-RAY | segmenttree Summary
kandi X-RAY | segmenttree Summary
A segment tree (interval tree) implementation in Python
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QUESTION
I've been trying to solve the FLIPCOIN question of CodeChef (https://www.codechef.com/problems/FLIPCOIN) but I always received the message Time Limit Exceeded.
The input is as follows: First comes a number n, the length of a row of coins, all turned tails up initially, and a number q, the number of tasks.
After that follow q tasks: updates, which have the form 0 A B and and should flip all coins in the range (inclusive) from A to B, and queries of the form 1 A B, where one should ouput the number of coins turned heads in the range from A to B.
I've already seen some solutions but I still don't know what is the problem with my code, is it because of the class? I would like to know why my code is so slow.
...ANSWER
Answered 2022-Feb-18 at 19:27The reason why your code is slow is that while your range queries take logarithmic time, your range updates take linear time. When updating a range of length n, you don't want to look at all n elements in that range. Instead, you want to make your updates lazy.
What does that mean?
If the range of a SegTree node is fully inside you queried range (left <= leftmost && rightmost <= right), you can just remember that you will need to update the coins in that range and recalculate the number of coins turned to heads (n_heads = rightmost - leftmost + 1 - n_heads) after the flip, but don't actually do anything else (especially not doing a recursive call)
Now when do you do the update? Always before doing a recursive call to the children, you will need to push the stored update in the current node to them. You can do this with an apply() method (this will flip all the coins in a SegTree node) and a push() method, which will apply a lazy update, if we need one.
This will reduce your runtime for a query from O(n) to O(log n)
So you need to do the following.
- add a
bool update = falsefield to your SegTree - add an apply and a push method
QUESTION
#include
#include
class SegmentTree final{
public:
template using data_type=T;
public:
template
explicit SegmentTree(const size_type& size);
};
ANSWER
Answered 2021-Sep-12 at 08:06There is no such thing as a inner template parameters for data members. If a data member depends on a type template parameter, such a parameter must be available in the signature of the class. That does not mean, however, that you need to specify all template parameters when instantiating a class, because, in c++17, they can be deduced by the constructor, see here.
Example:
QUESTION
I have the following code:
...ANSWER
Answered 2020-Apr-14 at 19:37You need to use an initaliser list
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Install segmenttree
You can use segmenttree like any standard Python library. You will need to make sure that you have a development environment consisting of a Python distribution including header files, a compiler, pip, and git installed. Make sure that your pip, setuptools, and wheel are up to date. When using pip it is generally recommended to install packages in a virtual environment to avoid changes to the system.
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