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Prevent RecursionMax stack exhaustion #97

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krotname wants to merge 1 commit into from
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Prevent RecursionMax stack exhaustion #97

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15 changes: 1 addition & 14 deletions src/main/java/other/RecursionMax.java
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Original file line number Diff line number Diff line change
Expand Up @@ -7,20 +7,7 @@
public class RecursionMax {

public static int recursionMax(List<Integer> array) {
if (array == null) {
return -1;
}
if (array.isEmpty()) {
return -1;
}
return recursionMax(array, 0, Integer.MIN_VALUE);
}

private static int recursionMax(List<Integer> array, int index, int currentMax) {
if (index == array.size()) {
return currentMax;
}
return recursionMax(array, index + 1, Math.max(currentMax, array.get(index)));
return max(array);
}

public static int max(List<Integer> array) {
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8 changes: 8 additions & 0 deletions src/test/java/other/RecursionMaxTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Stream;
import org.junit.jupiter.api.Tag;
Expand All @@ -29,6 +30,13 @@ void shouldNotMutateInputList() {
assertEquals(List.of(3, 8, 1, 5), values);
}

@Test
void shouldHandleLargeListsWithoutExhaustingTheStack() {
List<Integer> values = Collections.nCopies(100_000, 42);

assertEquals(42, RecursionMax.recursionMax(values));
}

private static Stream<Arguments> maxCases() {
return Stream.of(
Arguments.of(null, -1),
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