Maximum Bitwise XOR After Rearrangement — Python

# Time:  O(n)
# Space: O(1)

# greedy
class Solution(object):
    def maximumXor(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        cnt = [t.count('0'), t.count('1')]
        result = []
        for i in xrange(len(s)):
            x = ord(s[i])-ord('0')
            if cnt[x^1]:
                cnt[x^1] -= 1
                result.append('1')
            else:
                cnt[x] -= 1
                result.append('0')
        return "".join(result)