balanced string

balanced_string.py

def solution(s):
    n = len(s)

    ans = 999

    for i in range(n - 1):
        q = set([s[i]])
        for j in range(i + 1, n):
            q.add(s[j])
            #print(i, j , q, len(q))

            if len(q) % 2 == 0:
                if len(set([c.lower() for c in list(q)])) == len(q) // 2:
                    ans = min(ans, j - i + 1)
                    break

    if ans == 999:
        ans = -1

    return ans

print(solution('azABaabza')) # 5
print(solution('TacoCat'))   # -1
print(solution('AcZCbaBz'))   # 8
print(solution('abcdefg'))   # -1

print(solution('aAzABaGagAgabza'))