Add Fibonacci Search implementation in Java

JavaPracticeHacktoberfest.iml

@@ -4,6 +4,7 @@
     <output url="file://$MODULE_DIR$/bin" />
     <exclude-output />
     <content url="file://$MODULE_DIR$" />
+    <orderEntry type="jdk" jdkName="corretto-17" jdkType="JavaSDK" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
 </module>

Searching/FibonacciSearch.java

@@ -0,0 +1,94 @@
+/**
+ * Fibonacci Search Implementation in Java
+ *
+ * This class demonstrates the Fibonacci Search algorithm, an efficient
+ * searching technique for sorted arrays that uses Fibonacci numbers to
+ * divide the search space. The algorithm runs in O(log n) time.
+ *
+ * @author mtsagkl
+ */
+public class FibonacciSearch {
+    /**
+     * Executes the Fibonacci Search algorithm on a sorted array.
+     * This method uses Fibonacci numbers to split the search range .
+     *
+     * @param arr the sorted array in which the search is performed
+     * @param n   the array's size
+     * @param key the element to search for
+     * @return    the index of the key if found, otherwise -1
+     */
+    static int fibonacci_search(int arr[], int n,int key ){
+        int offset =-1;
+        int fm2=0;
+        int fm1=1;
+        int fm=fm1+fm2;
+
+        // find smallest Fibonacci number >= n
+        while(fm<n){
+            fm2=fm1;
+            fm1=fm;
+            fm=fm2+fm1;
+        }
+
+        while (fm>1){
+            int i;
+            if (offset+fm2<n-1){
+                i=offset+fm2;
+            }
+            else
+                i=n-1;
+
+            // if value is smaller, move right
+            if(arr[i]<key){
+                fm=fm1;
+                fm1=fm2;
+                fm2=fm-fm1;
+                offset=i;
+            }
+            // if value is greater, move left
+            else if(arr[i]>key){
+                fm=fm2;
+                fm1=fm1-fm2;
+                fm2=fm-fm1;
+            }
+            // value found
+            else
+                return i;
+        }
+        // check last possible position
+        if (fm1==1 && arr[offset+1]==key)
+            return offset +1;
+        return -1;  // not found
+    }
+
+    /**
+     * Main method to demonstrate Fibonacci search functionality
+     */
+    public static void main(String[] args) {
+        int n , key;
+        int arr[]={-15,-5,2,5,7,10,28,30,45,56};
+        System.out.print("Array's elements: ");
+        for (int i=0; i<arr.length; i++){
+            System.out.print(arr[i]+" ");
+        }
+        n = arr.length;
+
+        // Test with element in array
+        key = 10;
+        System.out.println("\nThe element to be searched: " + key);
+        int index = fibonacci_search(arr, n, key);
+        if(index >= 0)
+            System.out.println("Found at index " + index);
+        else
+            System.out.println("Not found");
+
+        // Test with element not in array
+        key = 20;
+        System.out.println("The element to be searched: " + key);
+        index = fibonacci_search(arr, n, key);
+        if(index >= 0)
+            System.out.println("Found at index " + index);
+        else
+            System.out.println("Not found");
+    }
+}