Add alternative solution in fibonacci-solution.js

Author: leivadev

10_fibonacci/solution/fibonacci-solution.js

@@ -1,12 +1,25 @@
 const fibonacci = function(count) {
     if (count < 0) return "OOPS";
     if (count === 0) return 0;
-    
-    const fib = [0, 1];
+
+    let firstPrev = 1;
+    let secondPrev = 0;
+
     for (let i = 2; i <= count; i++) {
-        fib[i] = fib[i - 1] + fib[i - 2];
+        let current = firstPrev + secondPrev;
+        secondPrev = firstPrev;
+        firstPrev = current;
     }
-    return fib[count];
+
+    return firstPrev;
+
 };
 
+// Another way to do it is by using an iterative approach with an array containing two values, 0 and 1.
+// const fib = [0, 1];
+// for (let i = 2; i <= count; i++) {
+//    fib[i] = fib[i - 1] + fib[i - 2];
+// }
+// return fib[count];
+
 module.exports = fibonacci;