comefrom: <qiyuangong>096_Unique_Binary_Search_Trees_1.py
code: def numTrees( n):
      dp = [0] * (n + 1)
      dp[0] = 1
      dp[1] = 1
      for level in range(2, n + 1):
          for root in range(1, level + 1):
              dp[level] += dp[level - root] * dp[root - 1]
      return dp[n]
masked: def sample_funcname ( var_0 ) :
      var_3 = [ 0 ] * ( var_0 + 1 )
      var_3 [ 0 ] = 1
      var_3 [ 1 ] = 1
      for var_6 in range ( 2 , var_0 + 1 ) :
          for var_7 in range ( 1 , var_6 + 1 ) :
              var_3 [ var_6 ] += var_3 [ var_6 - var_7 ] * var_3 [ var_7 - 1 ]
      return var_3 [ var_0 ]
  