Question

I was wondering if anyone can help me with the following method. I am not sure implement it. protected void writeToPostfix(char c) // Check the order settings on this based on the operator precedence settings while(operatorStack.) this.postfixExpression- this.postfixExpression C; Additional information: One example of this is for example during a conversion of an infix expression-( 2 +-3 ) * 5 when outputing in the console as a postfix expression it should return 21 3+5* instead of-2+3*9

In Java syntax

Answer 1

This is not the exact method, there are some modifications made but it does converts Infix expression to the postfix expression.

CODE:

import java.util.Stack;

import java.util.*;

class InfixtoPostfix
{  
static int Prec(char ch) {
switch (ch) {
case '+':
case '-':
return 1;
  case '*':
case '/':
return 2;
  case '^':
return 3;
}
return -1; }

// The main method that converts given infix expression
// to postfix expression.
static String WritetoPostfix(String exp) {
// initializing empty String for result
String result = new String("");
// initializing empty stack
Stack<Character> stack = new Stack<>();
   for (int i = 0; i<exp.length(); ++i) {
char c = exp.charAt(i);
   // If the scanned character is an operand, add it to output.
if (Character.isLetterOrDigit(c))
result += c;
// If the scanned character is an '(', push it to the stack.
else if (c == '(')
stack.push(c);
// If the scanned character is an ')', pop and output from the stack
// until an '(' is encountered.
else if (c == ')') {
while (!stack.isEmpty() && stack.peek() != '(')
result += stack.pop();
  if (!stack.isEmpty() && stack.peek() != '(')
return "Invalid Expression"; // invalid expression   
else
stack.pop(); }
else {
while (!stack.isEmpty() && Prec(c) <= Prec(stack.peek()))
result += stack.pop();
stack.push(c);
}  }

// pop all the operators from the stack
while (!stack.isEmpty())
result += stack.pop();
   return result; }
  

// Main Method
public static void main(String[] args)
{
String exp = "-(2*i+3)*5";
System.out.println(WritetoPostfix(exp));
}
}

Output :

Status Successfully executed Date 2019-04-14 07:17:25 Time 0.07 sec Mem 3153.92 kE Output 2i*3+5-