3335.js

/** ------------------------------------------------------------------------------
 * 
 * 3335. Total Characters in String After Transformations I
 * Topics: Hash Table, DP
 * https://leetcode.com/problems/total-characters-in-string-after-transformations-i/description/?envType=daily-question&envId=2025-05-13
 * 
 ------------------------------------------------------------------------------ */
var lengthAfterTransformations = function (s, t) {
  const MOD = 1000000007
  let cnt = Array.from({ length: 26 }).fill(0)
  for (const ch of s) {
    cnt[ch.charCodeAt(0) - "a".charCodeAt(0)]++
  }
  for (let round = 0; round < t; round++) {
    let nxt = Array.from({ length: 26 }).fill(0)
    nxt[0] = cnt[25]
    nxt[1] = (cnt[25] + cnt[0]) % MOD
    for (let i = 2; i < 26; i++) {
      nxt[i] = cnt[i - 1]
    }
    cnt = nxt
  }
  let ans = 0
  for (let i = 0; i < 26; i++) {
    ans = (ans + cnt[i]) % MOD
  }
  return ans
}

console.log(lengthAfterTransformations("abcyy", 2))