Merge pull request #4 from PauLopNun/PauLopNun-patch-5

Implement Fibonacci function using iteration

Author: PauLopNun

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
+}