comefrom: <qiyuangong>268_Missing_Number_2.py
code: def missingNumber( nums):
      res = len(nums)
      for i, v in enumerate(nums):
          res ^= i
          res ^= v
      return res
masked: def sample_funcname ( var_0 ) :
      var_2 = len ( var_0 )
      for var_4 , var_5 in enumerate ( var_0 ) :
          var_2 ^= var_4
          var_2 ^= var_5
      return var_2
  