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tkovs's solution

to Anagram in the ReasonML Track

Published at Oct 24 2020 · 0 comments
Instructions
Test suite
Solution

An anagram is a rearrangement of letters to form a new word. Given a word and a list of candidates, select the sublist of anagrams of the given word.

Given "listen" and a list of candidates like "enlists" "google" "inlets" "banana" the program should return a list containing "inlets".

Source

Inspired by the Extreme Startup game https://github.com/rchatley/extreme_startup

Building and testing

You will need the node package manager (npm) installed - download from here There is one time setup for each exercise, which may take a few minutes:

npm install

Open two shells, and in the first, start the build process.

npm start

In the second, start the tests running.

npm test

As you edit the code, the two processes will continually rebuild and rerun the tests.

Anagram_test.re

open Jest;
open Expect;
open Anagram;

describe("Anagram", () => {
  test("no matches", () =>
    expect(anagrams("diaper", ["hello", "world", "zombies", "pants"])) |> toEqual([])
  );
  test("detects two anagrams", () =>
    expect(anagrams("master", ["stream", "pigeon", "maters"])) |> toEqual(["stream", "maters"])
  );
  test("does not detect anagram subsets", () =>
    expect(anagrams("good", ["dog", "goody"]))  |> toEqual([])
  );
  test("detects anagram", () =>
    expect(anagrams("listen", ["enlists", "google", "inlets", "banana"]))  |> toEqual(["inlets"])
  );
  test("detects three anagrams", () =>
    expect(anagrams("allergy", ["gallery", "ballerina", "regally", "clergy", "largely", "leading"]))  |> toEqual(["gallery", "regally", "largely"])
  );
  test("detects multiple anagrams with different case", () =>
    expect(anagrams("nose", ["Eons", "ONES"]))  |> toEqual(["Eons", "ONES"])
  );
  test("does not detect non-anagrams with identical checksum", () =>
    expect(anagrams("mass", ["last"]))  |> toEqual([])
  );
  test("detects anagrams case-insensitively", () =>
    expect(anagrams("Orchestra", ["cashregister", "Carthorse", "radishes"]))  |> toEqual(["Carthorse"])
  );
  test("detects anagrams using case-insensitive subject", () =>
    expect(anagrams("Orchestra", ["cashregister", "carthorse", "radishes"])) |> toEqual(["carthorse"])
  );
  test("detects anagrams using case-insensitive possible matches", () =>
    expect(anagrams("orchestra", ["cashregister", "Carthorse", "radishes"])) |> toEqual(["Carthorse"])
  );
  test("does not detect a anagram if the original word is repeated", () =>
    expect(anagrams("go", ["go Go GO"])) |> toEqual([])
  );
  test("anagrams must use all letters exactly once", () =>
    expect(anagrams("tapper", ["patter"])) |> toEqual([])
  );
  test("words are not anagrams of themselves (case-insensitive)", () =>
    expect(anagrams("BANANA", ["BANANA", "Banana", "banana"])) |> toEqual([])
  );
  test("words other than themselves can be anagrams", () =>
    expect(anagrams("LISTEN", ["Listen", "Silent", "LISTEN"])) |> toEqual(["Silent"])
  );
})
let rec removeLetter = (word: string, letter: string): string => {
  open Js.String2

  let head = charAt(word, 0)
  let tail = substringToEnd(word, ~from=1)

  if (head == letter) {
    tail
  } else {
    if (length(tail) == 0) {
      head
    } else {
      head ++ removeLetter(tail, letter)
    }
  }
}

let rec isAnagramAux = (word1, word2) => {
  open Js.String2

  let word1length = length(word1)
  let word2length = length(word2)

  if (word1length != word2length) {
    false
  } else if (word1length == 0) {
    true 
  } else {
    let head = charAt(word1, 0)
    let tail = substringToEnd(word1, ~from=1)
    isAnagramAux(tail, removeLetter(word2, head))
  }
}

let isAnagram = (word1, word2) => {
  open Js.String2

  let uppercaseWord1 = toUpperCase(word1)
  let uppercaseWord2 = toUpperCase(word2)
  uppercaseWord1 != uppercaseWord2 && isAnagramAux(uppercaseWord1, uppercaseWord2)
}

let anagrams = (word, candidates) =>
  List.filter(candidate => isAnagram(candidate, word), candidates)

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