new_contents: class Solution(object):
      def findDuplicate(self, nums):
          """
          :type nums: List[int]
          :rtype: int
          """
          l, r = 1, len(nums) - 1
          while l < r:
              m = l + (r - l) / 2
              cnt = 0
              for num in nums:
                  if num <= m:
                      cnt += 1
              print l, r, m
              if cnt > m:
                  r = m
              else:
                  l = m + 1
          return l
  
subject: Add the bin search py version of FindtheDupNum