old_contents: """Leetcode 1. Two Sum
  
  URL: https://leetcode.com/problems/two-sum/description/
  
  Given an array of integers, return indices of the two numbers such that 
  they add up to a specific target.
  
  You may assume that each input would have exactly one solution, 
  and you may not use the same element twice.
  
  Example:
  Given nums = [2, 7, 11, 15], target = 9,
  
  Because nums[0] + nums[1] = 2 + 7 = 9,
  return [0, 1].
  """
  
  class Solution(object):
      def twoSum(self, nums, target):
          """
          :type nums: List[int]
          :type target: int
          :rtype: List[int]
          """
          lookup_dict = {}
          for i, num in enumerate(nums):
              if target - num in lookup_dict:
                  return [lookup_dict[target - num], i]
              lookup_dict[num] = i
          return []
  
  
  def main():
      print Solution().twoSum([2, 7, 11, 15], 9)
  
  if __name__ == '__main__':
      main()
  
new_contents: """Leetcode 1. Two Sum
  
  URL: https://leetcode.com/problems/two-sum/description/
  
  Given an array of integers, return indices of the two numbers such that 
  they add up to a specific target.
  
  You may assume that each input would have exactly one solution, 
  and you may not use the same element twice.
  
  Example:
  Given nums = [2, 7, 11, 15], target = 9,
  
  Because nums[0] + nums[1] = 2 + 7 = 9,
  return [0, 1].
  """
  
  class Solution(object):
      def twoSum(self, nums, target):
          """
          :type nums: List[int]
          :type target: int
          :rtype: List[int]
  
          Time complexity: O(n).
          Space complexity: O(n).
          """
          lookup_dict = {}
          for i, num in enumerate(nums):
              if target - num in lookup_dict:
                  return [lookup_dict[target - num], i]
              lookup_dict[num] = i
          return []
  
  
  def main():
      print Solution().twoSum([2, 7, 11, 15], 9)
  
  if __name__ == '__main__':
      main()
  
subject: Add time/space complexity