Fibonacci Search

Author: Faisal786111

Search/FibonacciSearch/main.c

@@ -0,0 +1,61 @@
+#include <stdio.h>
+
+int FibonacciSearch(int A[] , int n , int key){
+    // Generate Fibonacci Sequence until F(k) >= n 
+    int fibk_2 = 0; // f(k-2);
+    int fibk_1 = 1; // f(k-1);
+    int fibk = fibk_1 + fibk_2;
+    
+    while(fibk < n){
+        fibk_2 = fibk_1;
+        fibk_1 = fibk;
+        fibk = fibk_1 + fibk_2;
+    }
+    
+    // initialzie variable 
+    int offset = -1; // offset for the index 
+    int i;
+    
+    while(fibk > 1){
+         // Calculate the index to be checked
+        i = (offset + fibk_2 < n-1) ? offset + fibk_2 : n-1; // finding the min index
+        
+        // Compare with the target element
+        if(A[i] == key){
+            return i;
+        }else if(key > A[i]){
+             // Move left in the Fibonacci sequence  k = k-1
+            fibk = fibk_1;
+            fibk_1 = fibk_2;
+            fibk_2 = fibk - fibk_1;
+            offset = i;
+        }else {
+           // Move two steps left in the Fibonacci sequence  k = k-2
+           fibk = fibk_2;
+           fibk_1 = fibk_1 - fibk_2;
+           fibk_2 = fibk - fibk_1;
+        }
+    }
+    
+    // checking the last element manually 
+    if(fibk_1 && offset+1 < n && A[offset +1 ] == key){
+        return offset + 1; 
+    }
+    
+    return -1; // unseccussfull search
+}
+
+
+int main(){
+    int A[] = {5 , 6 , 7 , 8 , 9};
+    int n = sizeof(A) / sizeof(A[0]);
+    
+    int result = FibonacciSearch(A , n , 9);
+    
+    if(result == -1){
+        printf("%d" , result);
+    }else{
+        printf("%d" , result);
+    }
+    return 0;   
+}