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Suffix Array

Given a string s, sort all cyclic shifts of s. Formally produce a table p such that p[j]=i if s[i:]+s[:i] has rank j among all cyclic shifts.

PC Trees

A data structure representing all permutations satisfying constraints of the form: for a given set $S\subseteq\{0,1,\ldots,n-1\}$ the elements of the permutations on $\{0,1,\ldots,n-1\}$ have to be consecutive in circular manner.

Largest rectangle under an histogram

You are given an histogram and want to identify the area of the largest rectangle that fits under the histogram.

AI and LLM in education

In my new role as scientific advisor at the French Ministry of Education, I have recently been looking for meta-analyses and RCTs about impact of AI (and LLMs) in education.

Cover trees

Cover a tree with paths or caterpillars.

SWERC 2022 Practice Session - Bloggers

Abstract: Maintain two tables $t_0$, $t_1$. Updates: given $i,j,c$ increment $t_c$ between indices $i$ and $j$. After every update output $\sum_k \max{t_0[k],t_1[k]}$.

Deep Reinforcement Learning

Stable Baselines rely on TF 1.x but Stable Baselines v3 rely on PyTorch.

Organizing contests with judges


AlphaGo and Alpha Zero

In December 2016 we presented it at ENS Paris-Saclay with Étienne Simon but apparently I never wrote a blog post in the end.

Quadrangle Inequality trick for dynamic programs

Application: Given an ordered list of keys with frequencies, build a binary search tree on those keys which minimizes the average query cost.