2025-08-23 16:28:34 +0000 UTC

class Solution:
    def minChanges(self, n: int, k: int) -> int:
        res = 0
        if n < k:
            return -1
        while k > 0 or n > 0:
            n1, k1 = n & 1, k & 1
            if n1 != k1 and n1 == 0 and k1 == 1:
                return -1
            if n1 != k1:
                res += 1
            n >>= 1
            k >>= 1
        return res