2026-02-03 09:24:12 +0000 UTC

class Solution:
    def residuePrefixes(self, s: str) -> int:
        freqs = [0] * 26
        dist = 0
        res = 0
        for i in range(len(s)):
            target = (i + 1) % 3
            chr = ord(s[i]) - 97
            freqs[chr] += 1
            if freqs[chr] == 1:
                dist += 1
            if dist == target:
                res += 1
        return res