Java - Infix to Postfix Conversion
I have given here the source code in Java for InFix to PostFix Conversion with the help of Stack (Last In First Out) Data Struct implementation.
Source Code
import java.lang.*;
import java.util.*;
import java.io.*;
class InfixConverter
{
public static String ReadString()
{
try
{
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader reader = new BufferedReader(input);
return reader.readLine();
}
catch (Exception e)
{
e.printStackTrace();
return "";
}
}
public static int ReadInteger()
{
try
{
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader reader = new BufferedReader(input);
return Integer.parseInt(reader.readLine());
}
catch (Exception e)
{
e.printStackTrace();
return 0;
}
}
public static String InfixToPostfixConvert(String infixBuffer)
{
int priority = 0;
String postfixBuffer = "";
Stack s1 = new Stack();
for (int i = 0; i < infixBuffer.length(); i++)
{
char ch = infixBuffer.charAt(i);
if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
{
// check the precedence
if (s1.size() <= 0)
s1.push(ch);
else
{
Character chTop = (Character) s1.peek();
if (chTop == '*' || chTop == '/')
priority = 1;
else
priority = 0;
if (priority == 1)
{
if (ch == '+' || ch == '-')
{
postfixBuffer += s1.pop();
i--;
}
else
{ // Same
postfixBuffer += s1.pop();
i--;
}
}
else
{
if (ch == '+' || ch == '-')
{
postfixBuffer += s1.pop();
s1.push(ch);
}
else
s1.push(ch);
}
}
}
else
{
postfixBuffer += ch;
}
}
int len = s1.size();
for (int j = 0; j < len; j++)
postfixBuffer += s1.pop();
return postfixBuffer;
}
public static void main(String[] args)
{
String infixBuffer = "";
String postfixBuffer = "";
if(args.length == 1)
{
infixBuffer = args[0];
postfixBuffer = InfixToPostfixConvert(infixBuffer);
System.out.println("InFix :\t" + infixBuffer);
System.out.println("PostFix:\t" + postfixBuffer);
System.out.println();
}
else
{
infixBuffer = "a+b*c";
postfixBuffer = InfixToPostfixConvert(infixBuffer);
System.out.println("InFix :\t" + infixBuffer);
System.out.println("PostFix:\t" + postfixBuffer);
System.out.println();
infixBuffer = "a+b*c/d-e";
postfixBuffer = InfixToPostfixConvert(infixBuffer);
System.out.println("InFix :\t" + infixBuffer);
System.out.println("PostFix:\t" + postfixBuffer);
System.out.println();
infixBuffer = "a+b*c/d-e+f*h/i+j-k";
postfixBuffer = InfixToPostfixConvert(infixBuffer);
System.out.println("InFix :\t" + infixBuffer);
System.out.println("PostFix:\t" + postfixBuffer);
System.out.println();
}
}
}
Output
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