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fix: handle inputs like "2 +" in StackPostfixNotation #4262

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Merged
merged 1 commit into from
Jul 26, 2023
Merged

fix: handle inputs like "2 +" in StackPostfixNotation #4262

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3 changes: 3 additions & 0 deletions src/main/java/com/thealgorithms/others/StackPostfixNotation.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,9 @@ public static int postfixEvaluate(final String exp) {
if (tokens.hasNextInt()) {
s.push(tokens.nextInt()); // If int then push to stack
} else { // else pop top two values and perform the operation
if (s.size() < 2) {
throw new IllegalArgumentException("exp is not a proper postfix expression (too few arguments).");
}
int num2 = s.pop();
int num1 = s.pop();
String op = tokens.next();
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10 changes: 10 additions & 0 deletions src/test/java/com/thealgorithms/others/StackPostfixNotationTest.java
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Expand Up @@ -30,4 +30,14 @@ public void testIfEvaluateThrowsExceptionForInproperInput() {
public void testIfEvaluateThrowsExceptionForInputWithUnknownOperation() {
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 +"));
}
}