fix: handle constant inputs in `LongestIncreasingSubsequence::findLISLen' (#5160)

fix: handle constant inputs in `LongestIncreasingSubsequence::findLISLen`

src/test/java/com/thealgorithms/dynamicprogramming/LongestIncreasingSubsequenceTests.java

@@ -0,0 +1,49 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class LongestIncreasingSubsequenceTests {
+    @FunctionalInterface
+    public interface IntArrayToInt {
+        int apply(int[] array);
+    }
+
+    @ParameterizedTest
+    @MethodSource("testCases")
+    public void testLongestIncreasingSubsequence(final int expected, final int[] input, final IntArrayToInt method) {
+        assertEquals(expected, method.apply(input));
+    }
+
+    private static Stream<Arguments> testCases() {
+        final Object[][] testData = {
+            {0, new int[] {}},
+            {1, new int[] {1}},
+            {1, new int[] {2, 2}},
+            {1, new int[] {3, 3, 3}},
+            {1, new int[] {4, 4, 4, 4}},
+            {1, new int[] {5, 5, 5, 5, 5}},
+            {2, new int[] {1, 2}},
+            {2, new int[] {1, 2, 2, 2, 2}},
+            {2, new int[] {1, 0, 2}},
+            {3, new int[] {1, 10, 2, 30}},
+            {3, new int[] {5, 8, 3, 7, 9, 1}},
+            {6, new int[] {0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15}},
+            {4, new int[] {10, 9, 2, 5, 3, 7, 101, 18}},
+            {4, new int[] {10, 10, 9, 9, 2, 2, 5, 5, 3, 3, 7, 7, 101, 101, 18, 18}},
+            {4, new int[] {0, 1, 0, 3, 2, 3}},
+            {2, new int[] {1, 1, 2, 2, 2}},
+            {3, new int[] {1, 1, 2, 2, 2, 3, 3, 3, 3}},
+        };
+
+        final List<IntArrayToInt> methods = Arrays.asList(LongestIncreasingSubsequence::LIS, LongestIncreasingSubsequence::findLISLen);
+
+        return Stream.of(testData).flatMap(input -> methods.stream().map(method -> Arguments.of(input[0], input[1], method)));
+    }
+}