comments added

search/fibonacci_search.cpp

@@ -21,34 +21,48 @@
  * @returns if the array contains the value, returns an index of the element. otherwise -1.
  */
 int fibonacci_search(const std::vector<int> &arr, int value){
-    int last = 0, current = 1, offset = -1, index;
-    int length = arr.size();
-    int next = last + current;
+    // initialize last and current members of Fibonacci sequence 
+    int last = 0, current = 1;
+    int length = arr.size(); // array size
+    // next member of Fibonacci sequence which is "last" + "current"
+    int next = last + current; 
 
+    // "next" will store the smallest Fibonacci number greater or equal to "length"
     while(next < length){
         last = current;
         current = next;
         next = last + current;
     }
 
+    // "offset" is the end of eliminated range from front
+    int offset = -1, index;
+    // while loop until there are elements left to consider.
+    // when "next" becomes 1, last is equal to 0, so search is done,
+    // because arr[offset] will already be eliminated
     while(next > 1){
+        // check if "last" is valid location
         index = std::min(offset + last, length-1);
+        // if value is greater than the value at "index", eliminate the subarray from offset to index
         if(arr[index] < value){
             next = current;
             current = last;
             last = next - current;
             offset = index;
+        // if value is less than the value at "index", eliminate the subarray after index+1
         } else if(arr[index] > value){
             next = last;
             current = current - last;
             last = next - current;
+        // element is found
         } else {
             return index;
         }
     }
+    // comparing the last element
     if(current && !arr.empty() && arr[offset+1] == value){
         return offset+1;
     }
+    // value was not found, return -1
     return -1;
 }