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Postfix Evaluation #160

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Postfix Evaluation #160

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70 changes: 70 additions & 0 deletions Misc/PostfixEvaluation.java
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import java.util.Scanner;
import java.util.Stack;

/*
This Program will evaluate the value of given Postfix Expression
*/

public class PostfixEvaluation {
public static void main(String[] args) {
// Inserting Postfix Expression
System.out.println("Enter Postfix Expression");
Scanner s=new Scanner(System.in);
String exp=s.next();
int answer=PostEval(exp);
System.out.println("The Value of expression is : "+answer);
}

//Function to Evaluate Postfix Expression

private static int PostEval(String exp) {
Stack<Integer> helperStack=new Stack<>();
int i=0;
while(i<exp.length())
{
if(exp.charAt(i)=='*')
{
Integer A=helperStack.pop();
Integer B=helperStack.pop();
Integer C=B*A;
helperStack.push(C);
}
else if(exp.charAt(i)=='/')
{
Integer A=helperStack.pop();
Integer B=helperStack.pop();
Integer C=B/A;
helperStack.push(C);
}
else if(exp.charAt(i)=='^')
{
Integer A=helperStack.pop();
Integer B=helperStack.pop();
Integer C=(int) Math.pow((double) B,(double)A);
helperStack.push(C);
}
else if(exp.charAt(i)=='+')
{
Integer A=helperStack.pop();
Integer B=helperStack.pop();
Integer C=B+A;
helperStack.push(C);
}
else if(exp.charAt(i)=='-')
{
Integer A=helperStack.pop();
Integer B=helperStack.pop();
Integer C=B-A;
helperStack.push(C);
}
else
{
helperStack.push(Integer.parseInt(""+exp.charAt(i)));
}
i++;
}
int ans=helperStack.pop();
return ans;

}
}