Digital root/Multiplicative digital root: Difference between revisions

=={{header|Red}}==

<lang rebol>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

]</lang>

{{out}}

<pre>

123321 has multiplicative persistence 3 and MDR 8

7739 has multiplicative persistence 3 and MDR 8

893 has multiplicative persistence 3 and MDR 2

899998 has multiplicative persistence 2 and MDR 0

First five numbers with MDR of

0: 0 20 30 40 45

1: 1 11 111 1111 11111

2: 2 12 21 26 34

3: 3 13 31 113 131

4: 4 14 22 27 39

5: 5 15 35 51 53

6: 6 16 23 28 32

7: 7 17 71 117 171

8: 8 18 24 29 36

9: 9 19 33 91 119

</pre>