Chapter 14, Problem 3PP

Program Plan Intro

Infix to postfix expression

Program plan:

• Import necessary packages.
• Create a class “InfixToPostfix”,
  • Define the method “is_Operator ()” that accepts token as parameter,
    • Execute switch statement,
      • Match for the operators “+”, “-“, “*”, “/”, “^”, and, “%”.
        • Return “true”.
      • By default,
        • Return “false”.
  • Define the method “operator_Precedence()”,
    • Check whether the infix operator is “^”,
      • Return “true”.
    • Otherwise, check whether the right operator is “^”,
      • Return “false”.
    • Otherwise, check whether the infix operator is either “*” or “/” or “%”,
      • Return “true”.
    • Otherwise, check whether the right operator is either “*” or “/” or “%”,
      • Return “false”.
    • Return “true”.
  • Define the method “convert_InfixToPostfix()”,
    • Declare the empty string variable.
    • Construct stack object.
    • Insert “(“ into stack.
    • Execute till expression length,
      • Read character at the “i” position.
      • Check whether the character is a space,
        • Do nothing.
      • Otherwise check whether the character is either digit or “.” or letter,
        • Update the postfix expression.
      • Check whether the letter is “(“,
        • Insert into the stack.
      • Check whether letter is any operator,
        • Assign to the right operator.
        • Execute while loop,
        • • Updates postfix expression with space and character.
            • Updates postfix expression with space.
      • Check for “)”,
        • Execute while stack is non-empty,
        • • Updates postfix expression with space and characters.
          • Remove top of the stack.
            • Remove “(“.
            • Updates postfix expression with space.
      • Otherwise,
        • Print invalid expression message.
        • Break to exit the loop.
    • Execute while top of stack is not a “(“,
      • Updates postfix expression with space and character.
      • Remove top of stack.
    • Return postfix expression.
  • Define the method “main()”,
    • Construct object for “InfixToPostfix” class.
    • Create “Scanner” object.
    • Prompt the user to enter infix expression.
    • Get the infix expression from the user.
    • Call the method “convert-InfixToPostfix()”.
    • Print the postfix expression.