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Handle incorrect inputs in StackPostfixNotation (#4261)

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This commit is contained in:
Piotr Idzik
2023-07-26 08:20:56 +02:00
committed by GitHub
parent dec3b98e4b
commit 44dcebb699
2 changed files with 43 additions and 10 deletions
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20
src/main/java/com/thealgorithms/others/StackPostfixNotation.java
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@ -1,18 +1,14 @@
package com.thealgorithms.others;
import java.util.*;
import java.util.Scanner;
import java.util.Stack;
public class StackPostfixNotation {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String post = scanner.nextLine(); // Takes input with spaces in between eg. "1 21 +"
System.out.println(postfixEvaluate(post));
scanner.close();
public final class StackPostfixNotation {
private StackPostfixNotation() {
}
// Evaluates the given postfix expression string and returns the result.
public static int postfixEvaluate(String exp) {
public static int postfixEvaluate(final String exp) {
Stack<Integer> s = new Stack<Integer>();
Scanner tokens = new Scanner(exp);
@ -28,12 +24,16 @@ public class StackPostfixNotation {
case "+" -> s.push(num1 + num2);
case "-" -> s.push(num1 - num2);
case "*" -> s.push(num1 * num2);
default -> s.push(num1 / num2);
case "/" -> s.push(num1 / num2);
default -> throw new IllegalArgumentException("exp contains an unknown operation.");
}
// "+", "-", "*", "/"
}
}
tokens.close();
if (s.size() != 1) {
throw new IllegalArgumentException("exp is not a proper postfix expression.");
}
return s.pop();
}
}