Evaluate binomial coefficients: Difference between revisions

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@@ Line 1,381: / Line 1,381: @@
 =={{header|Kotlin}}==
-<lang scala>// version 1.0.5-2
+<lang scala>// version 2.0
-fun factorial(n: Int) = when {
-    n < 0 -> throw IllegalArgumentException("negative numbers not allowed")
-    else  -> {
-        var ans = 1L
-        for (i in 2..n) ans *= i
-        ans
-    }
-}
 fun binomial(n: Int, k: Int) = when {
@@ Line 1,396: / Line 1,387: @@
     n == k         -> 1L
     else           -> {
+        val kReduced = min(k, n - k)    // minimize number of steps
-        var ans = 1L
-        for (i in n - k + 1..n) ans *= i
+        var result = 1L
-        ans / factorial(k)
+        var numerator = n
+        var denominator = 1
+        while (denominator <= kReduced)
+            result = result * numerator-- / denominator++
+        result
     }
 }