improve fibonacchi examples [change in title]

main.py

@@ -1,17 +1,3 @@
-def nth_fibonacci(n):
-
-    # Base case: if n is 0 or 1, return n
-    if n <= 1:
-        return n
-
-    # Recursive case: sum of the two preceding Fibonacci numbers
-    return nth_fibonacci(n - 1) + nth_fibonacci(n - 2)
-
-n = 5
-result = nth_fibonacci(n)
-print(result)
-
-
 # Function to calculate the nth Fibonacci number using memoization
 def nth_fibonacci_util(n, memo):
 
@@ -71,3 +57,33 @@ def nth_fibonacci(n):
 n = 5
 result = nth_fibonacci(n)
 print(result)
+
+
+def nth_fibonacci(n):
+    if n <= 1:
+        return n
+
+    # To store the curr Fibonacci number
+    curr = 0
+
+    # To store the previous Fibonacci numbers
+    prev1 = 1
+    prev2 = 0
+
+    # Loop to calculate Fibonacci numbers from 2 to n
+    for i in range(2, n + 1):
+
+        # Calculate the curr Fibonacci number
+        curr = prev1 + prev2
+
+        # Update prev2 to the last Fibonacci number
+        prev2 = prev1
+
+        # Update prev1 to the curr Fibonacci number
+        prev1 = curr
+
+    return curr
+
+n = 5
+result = nth_fibonacci(n)
+print(result)