Add cross-correlation and auto-correlation (#4984)

src/test/java/com/thealgorithms/maths/AutoCorrelationTest.java

@@ -0,0 +1,37 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+/**
+ * Test class for AutoCorrelation class
+ *
+ * @author Athina-Frederiki Swinkels
+ * @version 2.0
+ */
+
+public class AutoCorrelationTest {
+
+    @ParameterizedTest
+    @CsvSource({"1;2;1;1, 1;3;5;7;5;3;1", "1;2;3, 3;8;14;8;3", "1.5;2.3;3.1;4.2, 6.3;14.31;23.6;34.79;23.6;14.31;6.3"})
+
+    public void testAutoCorrelationParameterized(String input, String expected) {
+        double[] array = convertStringToArray(input);
+        double[] expectedResult = convertStringToArray(expected);
+
+        double[] result = AutoCorrelation.autoCorrelation(array);
+
+        assertArrayEquals(expectedResult, result, 0.0001);
+    }
+
+    private double[] convertStringToArray(String input) {
+        String[] elements = input.split(";");
+        double[] result = new double[elements.length];
+        for (int i = 0; i < elements.length; i++) {
+            result[i] = Double.parseDouble(elements[i]);
+        }
+        return result;
+    }
+}

src/test/java/com/thealgorithms/maths/CrossCorrelationTest.java

@@ -0,0 +1,37 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+/**
+ * Test class for CrossCorrelation class
+ *
+ * @author Athina-Frederiki Swinkels
+ * @version 2.0
+ */
+public class CrossCorrelationTest {
+
+    @ParameterizedTest
+    @CsvSource({"1;2;1;1, 1;1;2;1, 1;4;6;6;5;2;1", "1;2;3, 1;2;3;4;5, 5;14;26;20;14;8;3", "1;2;3;4;5, 1;2;3, 3;8;14;20;26;14;5", "1.5;2.3;3.1;4.2, 1.1;2.2;3.3, 4.95;10.89;16.94;23.21;12.65;4.62"})
+
+    public void testCrossCorrelationParameterized(String input1, String input2, String expected) {
+        double[] array1 = convertStringToArray(input1);
+        double[] array2 = convertStringToArray(input2);
+        double[] expectedResult = convertStringToArray(expected);
+
+        double[] result = CrossCorrelation.crossCorrelation(array1, array2);
+
+        assertArrayEquals(expectedResult, result, 0.0001);
+    }
+
+    private double[] convertStringToArray(String input) {
+        String[] elements = input.split(";");
+        double[] result = new double[elements.length];
+        for (int i = 0; i < elements.length; i++) {
+            result[i] = Double.parseDouble(elements[i]);
+        }
+        return result;
+    }
+}