How to resolve the algorithm One of n lines in a file step by step in the OCaml programming language

Published on 12 May 2024 09:40 PM
#Ocaml

How to resolve the algorithm One of n lines in a file step by step in the OCaml programming language

Table of Contents

Problem Statement

A method of choosing a line randomly from a file: Is to:

Note: You may choose a smaller number of repetitions if necessary, but mention this up-front. Note: This is a specific version of a Reservoir Sampling algorithm: https://en.wikipedia.org/wiki/Reservoir_sampling

Let's start with the solution:

Step by Step solution about How to resolve the algorithm One of n lines in a file step by step in the OCaml programming language

Source code in the ocaml programming language

let one_of_n n =
  let rec aux i r =
    if i >= n then r else
      if Random.int (i + 1) = 0
      then aux (succ i) i
      else aux (succ i) r
  in
  aux 1 0

let test ~n ~trials =
  let ar = Array.make n 0 in
  for i = 1 to trials do
    let d = one_of_n n in
    ar.(d) <- succ ar.(d)
  done;
  Array.iter (Printf.printf " %d") ar;
  print_newline ()

let () =
  Random.self_init ();
  test ~n:10 ~trials:1_000_000

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