2025-08-24 12:21:21 +0000 UTC

class Solution:
    def findValidPair(self, s: str) -> str:
        freqs, n = [0] * 10, len(s)
        for i in range(n):
            freqs[int(s[i])] += 1
        for i in range(1, n):
            cur, prv = int(s[i]), int(s[i - 1])
            if cur != prv and freqs[cur] == cur and freqs[prv] == prv:
                return f"{prv}{cur}"
        return ""