Maximum Score Words Formed by Letters

export function maxScoreWords(words: string[], letters: string[], scores: number[]): number {
  const counts = new Array<number>(scores.length).fill(0);
  for (const letter of letters) {
    counts[getCharCode(letter)] += 1;
  }
 
  function backtrack(currentIndex: number): number {
    let maxScore = 0;
    for (let i = currentIndex; i < words.length; i++) {
      let totalScore = 0;
      let isValid = true;
      for (const char of words[i]) {
        const charCode = getCharCode(char);
        counts[charCode] -= 1;
        totalScore += scores[charCode];
        if (counts[charCode] < 0) {
          isValid = false;
        }
      }
 
      if (isValid) {
        totalScore += backtrack(i + 1);
        maxScore = Math.max(totalScore, maxScore);
      }
      for (const char of words[i]) {
        counts[getCharCode(char)] += 1;
        totalScore = 0;
      }
    }
    return maxScore;
  }
 
  return backtrack(0);
}
 
function getCharCode(char: string) {
  return char.charCodeAt(0) - 'a'.charCodeAt(0);
}