Research questions, open problems📈A question about Brownian motions, Airy integrals and random digraphs🧙A mysterious bijection✍️A hard derangement problem from an interviewBinary search done right✌️Binary search done right: introduction✌️Binary search done right: finding the median of a union in logarithmic time✌️Binary search done right: longest increasing subsequence in O(n log n)✌️Binary search done right: k-th non-present element in sorted array in O(log n)Notebooks♦️Clean code in Jupyter notebooks🧮Caching in IPython (notebooks)