1415.js

/** ------------------------------------------------------------------------------
 * 
 * 1415. The k-th Lexicographical String of All Happy Strings of Length n
 * Topics: Backtracking
 * https://leetcode.com/problems/the-k-th-lexicographical-string-of-all-happy-strings-of-length-n/?envType=daily-question&envId=2025-02-19
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number} n
 * @param {number} k
 * @return {string}
 */
var getHappyString = function (n, k) {
  let chars = "abc".split("")
  let solve = (i = 0, s = "") => {
    if (i == n) {
      k--
      if (k == 0) return s
      return ""
    }
    for (let c of chars) {
      if (c != s[s.length - 1]) {
        let rc = solve(i + 1, s + c)
        if (rc) return rc
      }
    }
    return ""
  }
  return solve()
}

console.log(getHappyString(1, 3))