---
categories: Data structures
---

## Problems
- [Count on a tree](http://www.spoj.com/problems/COT/)
- [K-th Number](http://www.spoj.com/problems/MKTHNUM/)
- [Sorting](https://www.codechef.com/problems/SORTING)
- [Observing the Tree](https://www.codechef.com/problems/QUERY)
- [Noble Knight's Path](http://codeforces.com/problemset/problem/226/E)
- [K-Query Online](http://www.spoj.com/problems/KQUERYO/) [^1]
- [Persistent Queue](http://codeforces.com/gym/100431)
- [Pork Barrel](https://open.kattis.com/problems/porkbarrel)

## See also
- [Segment tree]()
- [Persistent data structure]()

## External links
- [Persistent segment trees – Explained with spoj problems](https://blog.anudeep2011.com/persistent-segment-trees-explained-with-spoj-problems/)
- [Algorithm Gym :: Everything About Segment Trees](http://codeforces.com/blog/entry/15890)
- [Persistent Segment Trees HKU](https://i.cs.hku.hk/~provinci/training2016/notes4.pdf)

[^1]: Note that the test cases are a little bit shady, sometimes giving queries $i,j$ that don't satisfy $1\leq i\leq j\leq n$. **Blue.Mary** describes the correct behaviour in the comments.