SolutionTask3

class Solution {
  public static void main(String[] args) {
    Solution sol = new Solution();

    System.out.println(sol.solution("aaAbbcCABBc"));
    System.out.println(sol.solution("xyzXYZabcABC"));
    System.out.println(sol.solution("ABCabcAefG"));
  }

  public int solution(String letters) {
    int count = 0;
    Integer[] lastLowerCase = new Integer[26], firstUpperCase = new Integer[26];

    for (int i = 0; i < letters.length(); i++) {
      char charAtIndex = letters.charAt(i);

      // Is Lowercase?
      if (charAtIndex >= 'a' && charAtIndex <= 'z') {
        int charIndex = charAtIndex - 'a';
        lastLowerCase[charIndex] = i;
      }
      // Is Uppercase?
      else if (charAtIndex >= 'A' && charAtIndex <= 'Z') {
        int charIndex = charAtIndex - 'A';
        if (firstUpperCase[charIndex] == null)
          firstUpperCase[charIndex] = i;
      }
    }

    for (int i = 0; i < 26; i++) {
      if (lastLowerCase[i] != null && firstUpperCase[i] != null && lastLowerCase[i] < firstUpperCase[i]) {
        count++;
      }
    }

    return count;
  }
}