export function firstUniqueChar(s: string): number {
  const freq: Record<string, number> = {}

  for (const char of s) {
    freq[char] = (freq[char] || 0) + 1
  }

  for (let i = 0; i < s.length; i++) {
    if (freq[s[i]] === 1) {
      return i
    }
  }

  return -1;
}