Lua

fisher_yates_shuffle.lua

math.randomseed(os.time() + os.clock() * 100000)

--- Performs an in-place Fisher-Yates shuffle on the given array.
-- This function implements the Fisher-Yates shuffle algorithm.
-- It randomly shuffles the elements of the array in place, ensuring
-- that each permutation of the array is equally likely.
-- @tparam {[number]=any} arr The array to shuffle.
function fisher_yates_shuffle(arr)
  -- No need to shuffle if the array has less than 2 elements.
  if #arr < 2 then return end
  -- Start at the last index (#arr) and decrement to 2 to ensure all
  -- elements are shuffled.
  for outer = #arr, 2, -1 do
    local inner = math.random(outer)
    -- Perform in-place swapping to shuffle the elements.
    arr[outer], arr[inner] = arr[inner], arr[outer]
  end
end

foo.md

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