Write a java program that accept stack ADT converts infix expression to postfix form evaluates the postfix expression?

Answer 1

import java.io.*;
class stack
{
char stack1[]=new char[20];
int top;
void push(char ch)
{
top++;
stack1[top]=ch;
}
char pop()
{
char ch;
ch=stack1[top];
top--;
return ch;
}
int pre(char ch)
{
switch(ch)
{
case '-':return 1;
case '+':return 1;
case '*':return 2;
case '/':return 2;
}
return 0;
}
boolean operator(char ch)
{
if(ch=='/'ch=='*'ch=='+'ch=='-')
return true;
else
return false;
}
boolean isAlpha(char ch)
{
if(ch>='a'&&ch<='z'ch>='0'&&ch=='9')
return true;
else
return false;
}
void postfix(String str)
{
char output[]=new char[str.length()];
char ch;
int p=0,i;
for(i=0;i{
ch=str.charAt(i);
if(ch=='(')
{
push(ch);
}
else if(isAlpha(ch))
{
output[p++]=ch;
}
else if(operator(ch))
{
if(stack1[top]==0(pre(ch)>pre(stack1[top]))stack1[top]=='(')
{
push(ch);
}
}
else if(pre(ch)<=pre(stack1[top]))
{
output[p++]=pop();
push(ch);
}
else if(ch=='(')
{
while((ch=pop())!='(')
{
output[p++]=ch;
}
}
}
while(top!=0)
{
output[p++]=pop();
}
for(int j=0;j{
System.out.print(output[j]);
}
}
}

The main class in another notepad

import java.io.*;
class intopost
{
public static void main(String args[])throws Exception
{
String s;
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
stack b=new stack();
System.out.println("Enter input string");
s=br.readLine();
System.out.println("Input String:"+s);
System.out.println("Output String:");
b.postfix(s);
}
}

OUTPUT: Enter input string
a+b*c
Input String:a+b*c
Output String:
abc*+

Enter input string
a+(b*c)/d
Input String:a+(b*c)/d
Output String:
abc*d/)(+

Enter

abc*d