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PrefixEvaluationsAndConversions.java
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PrefixEvaluationsAndConversions.java
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package stacks;
import java.util.Scanner;
import java.util.Stack;
public class PrefixEvaluationsAndConversions {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String prefixExpression = scanner.nextLine();
Stack<Integer> evaluationStack = new Stack<>();
Stack<String> infixStack = new Stack<>();
Stack<String> postfixStack = new Stack<>();
for (int i=prefixExpression.length()-1; i>=0; i--) {
char ch = prefixExpression.charAt(i);
if (Character.isDigit(ch)) {
evaluationStack.push(ch - '0');
infixStack.push(String.valueOf(ch));
postfixStack.push(String.valueOf(ch));
} else {
evaluationStack.push(performPopOperation(evaluationStack.pop(), evaluationStack.pop(), ch));
infixStack.push(performPopOperationForInfix(infixStack.pop(), infixStack.pop(), ch));
postfixStack.push(performPopOperationForPostfix(postfixStack.pop(), postfixStack.pop(), ch));
}
}
System.out.println(evaluationStack.peek());
System.out.println(infixStack.peek());
System.out.println(postfixStack.peek());
}
private static String performPopOperationForPostfix(String val1, String val2, char op) {
return val1 + val2 + op;
}
private static String performPopOperationForInfix(String val1, String val2, char op) {
return val1 + op + val2;
}
private static Integer performPopOperation(Integer val1, Integer val2, char ch) {
int result = 0;
if (ch == '+') {
result = val1 + val2;
} else if (ch == '-') {
result = val1 - val2;
} else if (ch == '*') {
result = val1 * val2;
} else if (ch == '/') {
result = val1 / val2;
}
return result;
}
}