test-rot-words.js

const fs = require('fs')

const ALPHA = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('')
const RALPHA = new Map(ALPHA.map((e, i)=>[e, i]))
const rotBy = (word, n) =>  word.split('').map((l) => ALPHA[(RALPHA.get(l) + n) % ALPHA.length]).join('')
const rotByP = (word, n) =>  word.split('').map((l, i) => ALPHA[(RALPHA.get(l) + n + i) % ALPHA.length]).join('')

let list = fs.readFileSync('./mots.txt').toString().split('\n').filter(Boolean)
let set = new Set(list)
const stats = []

//for (let i = 0; i < 26; i++) {
  let rotN = 2//i
  let rotated = list.filter(mot => set.has(rotByP(mot, rotN))).map(mot => [mot, rotByP(mot, rotN)])
  
  //if (rotN === 13) rotated = rotated.filter(([mot], i, a) => a.find(([,e], i2)=> i2 > i && mot === e))

  let maxLen = rotated.reduce((ac,[mot]) => mot.length > ac ? mot.length : ac, 0)
  stats.push({rotN, maxLen, nb: rotated.length})

  console.log(rotated)
//}

console.table(stats)