Initial data commit

Task/Digital-root-Multiplicative-digital-root/Red/digital-root-multiplicative-digital-root.red

@@ -0,0 +1,39 @@
+Red ["Multiplicative digital root"]
+
+mdr: function [
+    "Returns a block containing the mdr and persistence of an integer"
+    n [integer!]
+][
+    persistence: 0
+    while [n > 10][
+        product: 1
+        m: n
+        while [m > 0][
+            product: m % 10 * product
+            m: to-integer m / 10
+        ]
+        persistence: persistence + 1
+        n: product
+    ]
+    reduce [n persistence]
+]
+
+foreach n [123321 7739 893 899998][
+    result: mdr n
+    print [pad n 6 "has multiplicative persistence" result/2 "and MDR" result/1]
+]
+
+print [newline "First five numbers with MDR of"]
+
+repeat i 10 [
+    prin rejoin [i - 1 ": "]
+    hits: n: 0
+    while [hits < 5][
+        if i - 1 = first mdr n [
+            prin pad n 5
+            hits: hits + 1
+        ]
+        n: n + 1
+    ]
+    prin newline
+]