parameters: (self, postfix)
return_statement: return stk.pop()
docstring: :type s: List[str]
          :rtype: int
docstring_summary: :type s: List[str]
          :rtype: int
docstring_tokens: : type s : List [ str ] : rtype : int
function: def buildTree(self, postfix):
          """
          :type s: List[str]
          :rtype: int
          """
          stk = []
          for c in postfix:
              if c.isdigit():
                  stk.append(NodeRecu(c))
              else:
                  node = NodeRecu(c)
                  node.right = stk.pop()
                  node.left = stk.pop()
                  stk.append(node)
          return stk.pop()
function_tokens: def buildTree ( self , postfix ) : stk = [ ] for c in postfix : if c . isdigit ( ) : stk . append ( NodeRecu ( c ) ) else : node = NodeRecu ( c ) node . right = stk . pop ( ) node . left = stk . pop ( ) stk . append ( node ) return stk . pop ( )