The book "Probabilistic Data Structures and Algorithms in Big Data Applications" is now available at Amazon and from local bookstores. More details at https://pdsa.gakhov.com In the presentation, I described common data structures and algorithms to estimate the number of distinct elements in a set (cardinality), such as Linear Counting, HyperLogLog, and HyperLogLog++. Each approach comes with some math that is behind it and simple examples to clarify the theory statements.