someodd

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
{-
Double Cola
https://codeforces.com/problemset/problem/82/A

EFFICIENCY REQUIREMENTS

time limit per test: 1 second
memory limit per test: 256 megabytes

someodd

{-
My attempt at a Tesla interview question:

Minimum number of characters to delete from a string so that each character
appears unique number of times. Note: You can delete all occurances of
characters.

eg: "aaaabbbb" -> 1 "a" or 1"b" would make "a" and "b" appear unique number of
times.
-}

someodd

{-
Advent of Code: Day 1
Part 1 and 2
https://adventofcode.com/2020/day/1
-}

-- Converted using a simple find/replace vim command.
puzzleInput =
  [ 1780
  , 1693

someodd

{-
Advent of Code: Day 2
Part 1 & 2
https://adventofcode.com/2020/day/2
-}


type PasswordData = ((Int, Int, Char), String)

someodd

import Control.Monad.Reader
import Data.Map as Map

data Expr = Lit Int | Var String | Add Expr Expr | Let (String, Expr) Expr

eval :: Expr -> Reader (Map String Int) Int
eval (Lit i) = pure i
eval (Var s) = do
  varMap <- ask
  case Map.lookup s varMap of

someodd

{-
I saw this posted on HackerNews:

"Most candidates cannot solve this interview problem."

https://twitter.com/Al_Grigor/status/1357028887209902088

> Most candidates cannot solve this interview problem:
> Input: "aaaabbbcca"
> Output: [("a", 4), ("b", 3), ("c", 2), ("a", 1)]

someodd

{-
# PROBLEM

A binary gap within a positive integer N is any maximal sequence of consecutive
zeros that is surrounded by ones at both ends in the binary representation of
N.

For example, number 9 has binary representation 1001 and contains a binary gap
of length 2. The number 529 has binary representation 1000010001 and contains
two binary gaps: one of length 4 and one of length 3. The number 20 has binary