Add Exponential Search (#2627)

Searches/ExponentalSearch.java

@@ -0,0 +1,59 @@
+package Searches;
+
+import java.util.Arrays;
+import java.util.Random;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.IntStream;
+
+import static java.lang.String.format;
+
+class ExponentialSearch implements SearchAlgorithm {
+
+    public static void main(String [] args) {
+        Random r = ThreadLocalRandom.current();
+
+        int size = 100;
+        int maxElement = 100000;
+
+        Integer[] integers =
+                IntStream.generate(() -> r.nextInt(maxElement))
+                        .limit(size)
+                        .sorted()
+                        .boxed()
+                        .toArray(Integer[]::new);
+
+        // The element that should be found
+        int shouldBeFound = integers[r.nextInt(size - 1)];
+
+        ExponentialSearch search = new ExponentialSearch();
+        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));
+
+    }
+
+    @Override
+    public <T extends Comparable<T>> int find(T[] array, T key) {
+        if (array[0] == key)
+            return 0;
+        if (array[array.length - 1] == key)
+            return array.length;
+
+        int range = 1;
+
+
+        while (range < array.length && array[range].compareTo(key) <= -1) {
+            range = range * 2;
+        }
+
+        return Arrays.binarySearch(array, range / 2, Math.min(range, array.length), key);
+    }
+}