comefrom: <qiyuangong>042_Trapping_Rain_Water_1.py
code: def rain_water( height, start, end):
      if end - start <= 1:
          return 0
      min_m = min(height[start], height[end])
      res = min_m * (end - start - 1)
      step = 0
      for index in range(start + 1, end):
          if height[index] > 0:
              step += height[index]
      return res - step
masked: def sample_funcname ( var_0 , var_1 , var_2 ) :
      if var_2 - var_1 <= 1 :
          return 0
      var_6 = min ( var_0 [ var_1 ] , var_0 [ var_2 ] )
      var_7 = var_6 * ( var_2 - var_1 - 1 )
      var_8 = 0
      for var_10 in range ( var_1 + 1 , var_2 ) :
          if var_0 [ var_10 ] > 0 :
              var_8 += var_0 [ var_10 ]
      return var_7 - var_8
  