From d30b486d5c820e47a5f7b29f1eca91ba2979455d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pau=20L=C3=B3pez=20N=C3=BA=C3=B1ez?=
 <paulopeznunez@gmail.com>
Date: Fri, 3 Oct 2025 04:05:14 +0200
Subject: [PATCH] Add iterative Fibonacci function to math directory

This PR adds an iterative function to compute the n-th Fibonacci number in Kotlin.
The function handles 0-based indices and returns Long to support larger numbers.
A main() function is included to test the implementation.
---
 src/main/kotlin/math/Fibonacci.kt | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 src/main/kotlin/math/Fibonacci.kt

diff --git a/src/main/kotlin/math/Fibonacci.kt b/src/main/kotlin/math/Fibonacci.kt
new file mode 100644
index 0000000..7fe5937
--- /dev/null
+++ b/src/main/kotlin/math/Fibonacci.kt
@@ -0,0 +1,22 @@
+/**
+ * Returns the n-th Fibonacci number (0-based index) using iteration.
+ */
+fun fibonacci(n: Int): Long {
+    require(n >= 0) { "n must be non-negative" }
+    if (n == 0) return 0
+    if (n == 1) return 1
+    var a = 0L
+    var b = 1L
+    for (i in 2..n) {
+        val temp = a + b
+        a = b
+        b = temp
+    }
+    return b
+}
+
+fun main() {
+    println("Fibonacci(0) = ${fibonacci(0)}")   // 0
+    println("Fibonacci(1) = ${fibonacci(1)}")   // 1
+    println("Fibonacci(10) = ${fibonacci(10)}") // 55
+}