old_contents: # Time:  O(1)
  # Space: O(1)
  
  # Given a positive integer, output its complement number.
  # The complement strategy is to flip the bits of its binary representation.
  #
  # Note:
  # The given integer is guaranteed to fit within the range of a 32-bit signed integer.
  # You could assume no leading zero bit in the integer’s binary representation.
  # Example 1:
  # Input: 5
  # Output: 2
  # Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
  # Example 2:
  # Input: 1
  # Output: 0
  # Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
  
  
  class Solution(object):
      def findComplement(self, num):
          """
          :type num: int
          :rtype: int
          """
          return 2 ** (len(bin(num)) - 2) - 1 - num
  
  
  class Solution2(object):
      def findComplement(self, num):
          i = 1
          while i <= num:
              i <<= 1
          return (i - 1) ^ num
  
new_contents: # Time:  O(1)
  # Space: O(1)
  
  # Given a positive integer, output its complement number.
  # The complement strategy is to flip the bits of its binary representation.
  #
  # Note:
  # The given integer is guaranteed to fit within the range of a 32-bit signed integer.
  # You could assume no leading zero bit in the integer’s binary representation.
  # Example 1:
  # Input: 5
  # Output: 2
  # Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
  # Example 2:
  # Input: 1
  # Output: 0
  # Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
  
  
  class Solution(object):
      def findComplement(self, num):
          """
          :type num: int
          :rtype: int
          """
          return 2 ** (len(bin(num)) - 2) - 1 - num
  
  
  class Solution2(object):
      def findComplement(self, num):
          i = 1
          while i <= num:
              i <<= 1
          return (i - 1) ^ num
  
  
  class Solution3(object):
      def findComplement(self, num):
          bits = '{0:b}'.format(num)
          complement_bits = ''.join('1' if bit == '0' else '0' for bit in bits)
          return int(complement_bits, 2)
  
subject: Add another solution for 'Number complement' problem