079-bit_flip.py

class Bits(object):

    MAX_BITS = 32

    def flip_bit(self, num):
        if num is None:
            raise TypeError('num cannot be None')
        if num == -1:
            return self.MAX_BITS
        if num == 0:
            return 1
        seen = self._build_seen_list(num)
        max_result = 0
        looking_for = 0
        for index, count in enumerate(seen):
            result = 0
            # Only look for zeroes
            if looking_for == 1:
                looking_for = not looking_for
                continue
            # First iteration, take trailing zeroes
            # or trailing ones into account
            if index == 0:
                if count != 0:
                    # Trailing zeroes
                    try:
                        result = seen[index + 1] + 1
                    except IndexError:
                        result = 1
            # Last iteration
            elif index == len(seen) - 1:
                result = 1 + seen[index - 1]
            else:
                # One zero
                if count == 1:
                    result = seen[index + 1] + seen[index - 1] + 1
                # Multiple zeroes
                else:
                    result = max(seen[index + 1], seen[index - 1]) + 1
            if result > max_result:
                max_result = result
            looking_for = not looking_for
        return max_result

    def _build_seen_list(self, num):
        seen = []
        looking_for = 0
        count = 0
        for _ in range(self.MAX_BITS):
            if num & 1 != looking_for:
                seen.append(count)
                looking_for = not looking_for
                count = 0
            count += 1
            num >>= 1
        seen.append(count)
        return seen