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refactor: StackPostfixNotation (#5400)

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Alex Klymenko 2024-08-26 15:38:33 +02:00 committed by GitHub
parent b70f077343
commit 64ff9b2efe
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2 changed files with 27 additions and 31 deletions
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13
src/main/java/com/thealgorithms/stacks/StackPostfixNotation.java
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@ -5,8 +5,15 @@ import java.util.Stack;
import java.util.function.BiFunction; import java.util.function.BiFunction;
/** /**
* @brief Utility class evaluating postix expressions, cf. https://en.wikipedia.org/wiki/Reverse_Polish_notation * Utility class for evaluating postfix expressions using integer arithmetic.
* @details The computation is done using Integers. * <p>
* Postfix notation, also known as Reverse Polish Notation (RPN), is a mathematical notation in which operators follow their operands.
* This class provides a method to evaluate expressions written in postfix notation.
* </p>
* <p>
* For more information on postfix notation, refer to
* <a href="https://en.wikipedia.org/wiki/Reverse_Polish_notation">Reverse Polish Notation (RPN) on Wikipedia</a>.
* </p>
*/ */
public final class StackPostfixNotation { public final class StackPostfixNotation {
private StackPostfixNotation() { private StackPostfixNotation() {
@ -55,7 +62,7 @@ public final class StackPostfixNotation {
* @exception IllegalArgumentException exp is not a valid postix expression. * @exception IllegalArgumentException exp is not a valid postix expression.
*/ */
public static int postfixEvaluate(final String exp) { public static int postfixEvaluate(final String exp) {
Stack<Integer> s = new Stack<Integer>(); Stack<Integer> s = new Stack<>();
consumeExpression(s, exp); consumeExpression(s, exp);
if (s.size() != 1) { if (s.size() != 1) {
throw new IllegalArgumentException("exp is not a proper postfix expression."); throw new IllegalArgumentException("exp is not a proper postfix expression.");

45
src/test/java/com/thealgorithms/stacks/StackPostfixNotationTest.java
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@ -1,43 +1,32 @@
package com.thealgorithms.stacks; package com.thealgorithms.stacks;
import static java.util.Map.entry;
import static org.junit.jupiter.api.Assertions.assertEquals; import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows; import static org.junit.jupiter.api.Assertions.assertThrows;
import java.util.Map; import java.util.stream.Stream;
import org.junit.jupiter.api.Test; import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;
public class StackPostfixNotationTest { public class StackPostfixNotationTest {
@Test
public void testEvaluate() { @ParameterizedTest
final Map<String, Integer> testCases = Map.ofEntries(entry("1 1 +", 2), entry("2 3 *", 6), entry("6 2 /", 3), entry("-5 -2 -", -3), entry("5 2 + 3 *", 21), entry("-5", -5)); @MethodSource("provideValidTestCases")
for (final var tc : testCases.entrySet()) { void testEvaluate(String expression, int expected) {
assertEquals(tc.getValue(), StackPostfixNotation.postfixEvaluate(tc.getKey())); assertEquals(expected, StackPostfixNotation.postfixEvaluate(expression));
}
} }
@Test static Stream<Arguments> provideValidTestCases() {
public void testIfEvaluateThrowsExceptionForEmptyInput() { return Stream.of(Arguments.of("1 1 +", 2), Arguments.of("2 3 *", 6), Arguments.of("6 2 /", 3), Arguments.of("-5 -2 -", -3), Arguments.of("5 2 + 3 *", 21), Arguments.of("-5", -5));
assertThrows(IllegalArgumentException.class, () -> StackPostfixNotation.postfixEvaluate(""));
} }
@Test @ParameterizedTest
public void testIfEvaluateThrowsExceptionForInproperInput() { @MethodSource("provideInvalidTestCases")
assertThrows(IllegalArgumentException.class, () -> StackPostfixNotation.postfixEvaluate("3 3 3")); void testEvaluateThrowsException(String expression) {
assertThrows(IllegalArgumentException.class, () -> StackPostfixNotation.postfixEvaluate(expression));
} }
@Test static Stream<Arguments> provideInvalidTestCases() {
public void testIfEvaluateThrowsExceptionForInputWithUnknownOperation() { return Stream.of(Arguments.of(""), Arguments.of("3 3 3"), Arguments.of("3 3 !"), Arguments.of("+"), Arguments.of("2 +"));
assertThrows(IllegalArgumentException.class, () -> StackPostfixNotation.postfixEvaluate("3 3 !"));
}
@Test
public void testIfEvaluateThrowsExceptionForInputWithTooFewArgsA() {
assertThrows(IllegalArgumentException.class, () -> StackPostfixNotation.postfixEvaluate("+"));
}
@Test
public void testIfEvaluateThrowsExceptionForInputWithTooFewArgsB() {
assertThrows(IllegalArgumentException.class, () -> StackPostfixNotation.postfixEvaluate("2 +"));
} }
} }