Add tests, remove main, improve docs in InterpolationSearch (TheAlgorithms#5666)

Author: Hardvan

DIRECTORY.md

@@ -1004,6 +1004,7 @@
             * [ExponentialSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/ExponentialSearchTest.java)
             * [FibonacciSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/FibonacciSearchTest.java)
             * [HowManyTimesRotatedTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/HowManyTimesRotatedTest.java)
+            * [InterpolationSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/InterpolationSearchTest.java)
             * [KMPSearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/KMPSearchTest.java)
             * [OrderAgnosticBinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/OrderAgnosticBinarySearchTest.java)
             * [PerfectBinarySearchTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/searches/PerfectBinarySearchTest.java)

src/main/java/com/thealgorithms/searches/InterpolationSearch.java

@@ -1,25 +1,31 @@
 package com.thealgorithms.searches;
 
-import java.util.Arrays;
-import java.util.Random;
-import java.util.stream.IntStream;
-
 /**
- * Interpolation search algorithm implementation
+ * InterpolationSearch is an algorithm that searches for a target value within a sorted array
+ * by estimating the position based on the values at the corners of the current search range.
+ *
+ * <p>
+ * The performance of this algorithm can vary:
+ * - Worst-case performance: O(n)
+ * - Best-case performance: O(1)
+ * - Average performance: O(log(log(n))) if the elements are uniformly distributed; otherwise O(n)
+ * - Worst-case space complexity: O(1)
+ * </p>
  *
  * <p>
- * Worst-case performance O(n) Best-case performance O(1) Average performance
- * O(log(log(n))) if the elements are uniformly distributed if not O(n)
- * Worst-case space complexity O(1)
+ * This search algorithm requires the input array to be sorted.
+ * </p>
  *
  * @author Podshivalov Nikita (https://github.com/nikitap492)
  */
 class InterpolationSearch {
 
     /**
-     * @param array is a sorted array
-     * @param key is a value what shoulb be found in the array
-     * @return an index if the array contains the key unless -1
+     * Finds the index of the specified key in a sorted array using interpolation search.
+     *
+     * @param array The sorted array to search.
+     * @param key The value to search for.
+     * @return The index of the key if found, otherwise -1.
      */
     public int find(int[] array, int key) {
         // Find indexes of two corners
@@ -48,23 +54,4 @@ public int find(int[] array, int key) {
         }
         return -1;
     }
-
-    // Driver method
-    public static void main(String[] args) {
-        Random r = new Random();
-        int size = 100;
-        int maxElement = 100000;
-        int[] integers = IntStream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray();
-
-        // the element that should be found
-        int shouldBeFound = integers[r.nextInt(size - 1)];
-
-        InterpolationSearch search = new InterpolationSearch();
-        int atIndex = search.find(integers, shouldBeFound);
-
-        System.out.printf("Should be found: %d. Found %d at index %d. An array length %d%n", shouldBeFound, integers[atIndex], atIndex, size);
-
-        int toCheck = Arrays.binarySearch(integers, shouldBeFound);
-        System.out.printf("Found by system method at an index: %d. Is equal: %b%n", toCheck, toCheck == atIndex);
-    }
 }

src/test/java/com/thealgorithms/searches/InterpolationSearchTest.java

@@ -0,0 +1,90 @@
+package com.thealgorithms.searches;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.stream.IntStream;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the InterpolationSearch class.
+ */
+class InterpolationSearchTest {
+
+    /**
+     * Test for basic interpolation search functionality when the element is found.
+     */
+    @Test
+    void testInterpolationSearchFound() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = {1, 2, 4, 8, 16, 32, 64, 128, 256, 512};
+        int key = 128;
+        int expectedIndex = 7; // Index of the key in the array
+        assertEquals(expectedIndex, interpolationSearch.find(array, key), "The index of the found element should be 7.");
+    }
+
+    /**
+     * Test for interpolation search when the element is not present in the array.
+     */
+    @Test
+    void testInterpolationSearchNotFound() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = {1, 2, 4, 8, 16};
+        int key = 6; // Element not present in the array
+        assertEquals(-1, interpolationSearch.find(array, key), "The element should not be found in the array.");
+    }
+
+    /**
+     * Test for interpolation search with the first element as the key.
+     */
+    @Test
+    void testInterpolationSearchFirstElement() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = {1, 2, 4, 8, 16};
+        int key = 1; // First element
+        assertEquals(0, interpolationSearch.find(array, key), "The index of the first element should be 0.");
+    }
+
+    /**
+     * Test for interpolation search with a single element not present.
+     */
+    @Test
+    void testInterpolationSearchSingleElementNotFound() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = {1};
+        int key = 2; // Key not present
+        assertEquals(-1, interpolationSearch.find(array, key), "The element should not be found in the array.");
+    }
+
+    /**
+     * Test for interpolation search with an empty array.
+     */
+    @Test
+    void testInterpolationSearchEmptyArray() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = {}; // Empty array
+        int key = 1; // Key not present
+        assertEquals(-1, interpolationSearch.find(array, key), "The element should not be found in an empty array.");
+    }
+
+    /**
+     * Test for interpolation search on large uniformly distributed array.
+     */
+    @Test
+    void testInterpolationSearchLargeUniformArray() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = IntStream.range(0, 10000).map(i -> i * 2).toArray(); // Array from 0 to 19998, step 2
+        int key = 9998; // Last even number in the array
+        assertEquals(4999, interpolationSearch.find(array, key), "The index of the last element should be 4999.");
+    }
+
+    /**
+     * Test for interpolation search on large non-uniformly distributed array.
+     */
+    @Test
+    void testInterpolationSearchLargeNonUniformArray() {
+        InterpolationSearch interpolationSearch = new InterpolationSearch();
+        int[] array = {1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144}; // Fibonacci numbers
+        int key = 21; // Present in the array
+        assertEquals(6, interpolationSearch.find(array, key), "The index of the found element should be 6.");
+    }
+}