Family Day update

Task/Evaluate-binomial-coefficients/Java/evaluate-binomial-coefficients-1.java

@@ -1,18 +1,71 @@
-public class Binomial
-{
-    private static long binomial(int n, int k)
-    {
-        if (k>n-k)
-            k=n-k;
+public class Binomial {
 
-        long b=1;
-        for (int i=1, m=n; i<=k; i++, m--)
-            b=b*m/i;
-        return b;
+    // precise, but may overflow and then produce completely incorrect results
+    private static long binomialInt(int n, int k) {
+        if (k > n - k)
+            k = n - k;
+
+        long binom = 1;
+        for (int i = 1; i <= k; i++)
+            binom = binom * (n + 1 - i) / i;
+        return binom;
     }
 
-    public static void main(String[] args)
-    {
-        System.out.println(binomial(5, 3));
+    // same as above, but with overflow check
+    private static Object binomialIntReliable(int n, int k) {
+        if (k > n - k)
+            k = n - k;
+
+        long binom = 1;
+        for (int i = 1; i <= k; i++) {
+            try {
+                binom = Math.multiplyExact(binom, n + 1 - i) / i;
+            } catch (ArithmeticException e) {
+                return "overflow";
+            }
+        }
+        return binom;
+    }
+
+    // using floating point arithmetic, larger numbers can be calculated,
+    // but with reduced precision
+    private static double binomialFloat(int n, int k) {
+        if (k > n - k)
+            k = n - k;
+
+        double binom = 1.0;
+        for (int i = 1; i <= k; i++)
+            binom = binom * (n + 1 - i) / i;
+        return binom;
+    }
+
+    // slow, hard to read, but precise
+    private static BigInteger binomialBigInt(int n, int k) {
+        if (k > n - k)
+            k = n - k;
+
+        BigInteger binom = BigInteger.ONE;
+        for (int i = 1; i <= k; i++) {
+            binom = binom.multiply(BigInteger.valueOf(n + 1 - i));
+            binom = binom.divide(BigInteger.valueOf(i));
+        }
+        return binom;
+    }
+
+    private static void demo(int n, int k) {
+        List<Object> data = Arrays.asList(
+                n,
+                k,
+                binomialInt(n, k),
+                binomialIntReliable(n, k),
+                binomialFloat(n, k),
+                binomialBigInt(n, k));
+
+        System.out.println(data.stream().map(Object::toString).collect(Collectors.joining("\t")));
+    }
+
+    public static void main(String[] args) {
+        demo(5, 3);
+        demo(1000, 300);
     }
 }