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_1 = len ( var_0 )
      for var_2 , var_3 in enumerate ( var_0 ) :
          var_1 ^= var_2
          var_1 ^= var_3
      return var_1
  