Change project structure to a Maven Java project + Refactor (#2816)

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

@@ -0,0 +1,90 @@
+package com.thealgorithms.searches;
+
+import static java.lang.String.format;
+
+import java.util.Arrays;
+import java.util.Random;
+import java.util.stream.Stream;
+import com.thealgorithms.devutils.searches.SearchAlgorithm;
+
+/**
+ * A ternary search algorithm is a technique in computer science for finding the
+ * minimum or maximum of a unimodal function The algorithm determines either
+ * that the minimum or maximum cannot be in the first third of the domain or
+ * that it cannot be in the last third of the domain, then repeats on the
+ * remaining third.
+ *
+ * <p>
+ * Worst-case performance Θ(log3(N)) Best-case performance O(1) Average
+ * performance Θ(log3(N)) Worst-case space complexity O(1)
+ *
+ * @author Podshivalov Nikita (https://github.com/nikitap492)
+ * @see SearchAlgorithm
+ * @see IterativeBinarySearch
+ */
+public class TernarySearch implements SearchAlgorithm {
+
+    /**
+     * @param arr The **Sorted** array in which we will search the element.
+     * @param value The value that we want to search for.
+     * @return The index of the element if found. Else returns -1.
+     */
+    @Override
+    public <T extends Comparable<T>> int find(T[] arr, T value) {
+        return ternarySearch(arr, value, 0, arr.length - 1);
+    }
+
+    /**
+     * @param arr The **Sorted** array in which we will search the element.
+     * @param key The value that we want to search for.
+     * @param start The starting index from which we will start Searching.
+     * @param end The ending index till which we will Search.
+     * @return Returns the index of the Element if found. Else returns -1.
+     */
+    private <T extends Comparable<T>> int ternarySearch(T[] arr, T key, int start, int end) {
+        if (start > end) {
+            return -1;
+        }
+        /* First boundary: add 1/3 of length to start */
+        int mid1 = start + (end - start) / 3;
+        /* Second boundary: add 2/3 of length to start */
+        int mid2 = start + 2 * (end - start) / 3;
+
+        if (key.compareTo(arr[mid1]) == 0) {
+            return mid1;
+        } else if (key.compareTo(arr[mid2]) == 0) {
+            return mid2;
+        } /* Search the first (1/3) rd part of the array.*/ else if (key.compareTo(arr[mid1]) < 0) {
+            return ternarySearch(arr, key, start, --mid1);
+        } /* Search 3rd (1/3)rd part of the array */ else if (key.compareTo(arr[mid2]) > 0) {
+            return ternarySearch(arr, key, ++mid2, end);
+        } /* Search middle (1/3)rd part of the array */ else {
+            return ternarySearch(arr, key, mid1, mid2);
+        }
+    }
+
+    public static void main(String[] args) {
+        // just generate data
+        Random r = new Random();
+        int size = 100;
+        int maxElement = 100000;
+        Integer[] integers
+                = Stream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray(Integer[]::new);
+
+        // the element that should be found
+        Integer shouldBeFound = integers[r.nextInt(size - 1)];
+
+        TernarySearch search = new TernarySearch();
+        int atIndex = search.find(integers, shouldBeFound);
+
+        System.out.println(
+                format(
+                        "Should be found: %d. Found %d at index %d. An array length %d",
+                        shouldBeFound, integers[atIndex], atIndex, size));
+
+        int toCheck = Arrays.binarySearch(integers, shouldBeFound);
+        System.out.println(
+                format(
+                        "Found by system method at an index: %d. Is equal: %b", toCheck, toCheck == atIndex));
+    }
+}