Colorful numbers
A colorful number is a non-negative base 10 integer where the product of every sub group of consecutive digits is unique.
- E.G.
24753 is a colorful number. 2, 4, 7, 5, 3, (2×4)8, (4×7)28, (7×5)35, (5×3)15, (2×4×7)56, (4×7×5)140, (7×5×3)105, (2×4×7×5)280, (4×7×5×3)420, (2×4×7×5×3)840
Every product is unique.
2346 is not a colorful number. 2, 3, 4, 6, (2×3)6, (3×4)12, (4×6)24, (2×3×4)48, (3×4×6)72, (2×3×4×6)144
The product 6 is repeated.
Single digit numbers are considered to be colorful. A colorful number larger than 9 cannot contain a repeated digit, the digit 0 or the digit 1. As a consequence, there is a firm upper limit for colorful numbers; no colorful number can have more than 8 digits.
- Task
- Write a routine (subroutine, function, procedure, whatever it may be called in your language) to test if a number is a colorful number or not.
- Use that routine to find all of the colorful numbers less than 100.
- Use that routine to find the largest possible colorful number.
- Stretch
- Find and display the count of colorful numbers in each order of magnitude.
- Find and show the total count of all colorful numbers.
Colorful numbers have no real number theory application. They are more a recreational math puzzle than a useful tool.
J
<lang J> colorful=: {{(-:~.);<@(*/\)\. 10 #.inv y}}"0
I.colorful i.100
0 1 2 3 4 5 6 7 8 9 23 24 25 26 27 28 29 32 34 35 36 37 38 39 42 43 45 46 47 48 49 52 53 54 56 57 58 59 62 63 64 65 67 68 69 72 73 74 75 76 78 79 82 83 84 85 86 87 89 92 93 94 95 96 97 98
C=: I.colorful <.i.1e8 >./C
98746253
(~.,. #/.~) 10 <.@^. C
__ 1
0 9 1 56 2 328 3 1540 4 5514 5 13956 6 21596 7 14256 #C
57256</lang>
Phix
You can run this online here.
with javascript_semantics function colourful(integer n) if n<10 then return n>=0 end if sequence digits = sq_sub(sprintf("%d",n),'0'), ud = unique(deep_copy(digits)) integer ln = length(digits) if ud[1]<=1 or length(ud)!=ln then return false end if for i=1 to ln-1 do for j=i+1 to ln do atom prod = product(digits[i..j]) if find(prod,ud) then return false end if ud &= prod end for end for return true end function atom t0 = time() sequence cn = apply(true,sprintf,{{"%2d"},filter(tagset(100,0),colourful)}) printf(1,"The %d colourful numbers less than 100 are:\n%s\n", {length(cn),join_by(cn,1,10," ")}) sequence count = repeat(0,8), used = repeat(false,10) integer largestcn = 0 procedure count_colourful(integer taken=0, string n="") if taken=0 then for digit='0' to '9' do integer dx = digit-'0'+1 used[dx] = true count_colourful(iff(digit<'2'?9:1),""&digit) used[dx] = false end for else integer nn = to_integer(n) if colourful(nn) then integer ln = length(n) count[ln] += 1 if nn>largestcn then largestcn = nn end if end if if taken<9 then for digit='2' to '9' do integer dx = digit-'0'+1 if not used[dx] then used[dx] = true count_colourful(taken+1,n&digit) used[dx] = false end if end for end if end if end procedure count_colourful() printf(1,"The largest possible colourful number is: %,d\n\n",largestcn) atom pow = 10 for dc=1 to length(count) do printf(1," %d digit colourful number count: %,6d - %7.3f%%\n", {dc, count[dc], 100*count[dc]/pow}) pow = iff(pow=10?90:pow*10) end for printf(1,"\nTotal colourful numbers: %,d\n", sum(count)) ?elapsed(time()-t0)
- Output:
The 66 colourful numbers less than 100 are: 0 1 2 3 4 5 6 7 8 9 23 24 25 26 27 28 29 32 34 35 36 37 38 39 42 43 45 46 47 48 49 52 53 54 56 57 58 59 62 63 64 65 67 68 69 72 73 74 75 76 78 79 82 83 84 85 86 87 89 92 93 94 95 96 97 98 The largest possible colourful number is: 98,746,253 1 digit colourful number count: 10 - 100.000% 2 digit colourful number count: 56 - 62.222% 3 digit colourful number count: 328 - 36.444% 4 digit colourful number count: 1,540 - 17.111% 5 digit colourful number count: 5,514 - 6.127% 6 digit colourful number count: 13,956 - 1.551% 7 digit colourful number count: 21,596 - 0.240% 8 digit colourful number count: 14,256 - 0.016% Total colourful numbers: 57,256 "1.9s"
Raku
<lang perl6>sub is-colorful (Int $n) {
return True if 0 <= $n <= 9;
return False if $n.contains(0) || $n.contains(1) || $n < 0;
my @digits = $n.comb;
my %sums = @digits.Bag;
return False if %sums.values.max > 1;
for 2..@digits -> $group {
@digits.rotor($group => 1 - $group).map: { %sums{ [×] $_ }++ }
return False if %sums.values.max > 1;
}
True
}
put "Colorful numbers less than 100:\n" ~ (^100).race.grep( &is-colorful).batch(10)».fmt("%2d").join: "\n";
my ($start, $total) = 23456789, 10;
print "\nLargest magnitude colorful number: "; .put and last if .Int.&is-colorful for $start.flip … $start;
put "\nCount of colorful numbers for each order of magnitude:\n" ~
"1 digit colorful number count: $total - 100%";
for 2..8 {
put "$_ digit colorful number count: ",
my $c = +(flat $start.comb.combinations($_).map: {.permutations».join».Int}).race.grep( &is-colorful ),
" - {($c / (exp($_,10) - exp($_-1,10) ) * 100).round(.001)}%";
$total += $c;
}
say "\nTotal colorful numbers: $total";</lang>
- Output:
Colorful numbers less than 100: 0 1 2 3 4 5 6 7 8 9 23 24 25 26 27 28 29 32 34 35 36 37 38 39 42 43 45 46 47 48 49 52 53 54 56 57 58 59 62 63 64 65 67 68 69 72 73 74 75 76 78 79 82 83 84 85 86 87 89 92 93 94 95 96 97 98 Largest magnitude colorful number: 98746253 Count of colorful numbers for each order of magnitude: 1 digit colorful number count: 10 - 100% 2 digit colorful number count: 56 - 62.222% 3 digit colorful number count: 328 - 36.444% 4 digit colorful number count: 1540 - 17.111% 5 digit colorful number count: 5514 - 6.127% 6 digit colorful number count: 13956 - 1.551% 7 digit colorful number count: 21596 - 0.24% 8 digit colorful number count: 14256 - 0.016% Total colorful numbers: 57256
Wren
<lang ecmascript>import "./math" for Int, Nums import "./set" for Set import "./seq" for Lst import "./fmt" for Fmt
var isColorful = Fn.new { |n|
if (n < 0) return false
if (n < 10) return true
var digits = Int.digits(n)
if (digits.contains(0) || digits.contains(1)) return false
var set = Set.new(digits)
var dc = digits.count
if (set.count < dc) return false
for (k in 2..dc) {
for (i in 0..dc-k) {
var prod = 1
for (j in i..i+k-1) prod = prod * digits[j]
if (set.contains(prod)) return false
set.add(prod)
}
}
return true
}
System.print("The colorful numbers less than 100 are:") var colorful = (0..99).where { |i| isColorful.call(i) }.toList for (chunk in Lst.chunks(colorful, 10)) Fmt.print("$2d", chunk)
var largest = 0 System.print("\nThe largest possible colorful number is:") for (i in 1e8-1..0) {
if (isColorful.call(i)) {
Fmt.print("$,d", i)
largest = i
break
}
}
var count = List.filled(9, 0) var dc = 1 var pow = 10 System.print("\nCount of colorful numbers for each order of magnitude:") var i = 0 while (true) {
if (dc > 1) {
var rem = i % 10
if (rem == 0 || rem == 1) {
i = i + 2 - rem
continue
}
}
if (isColorful.call(i)) count[dc] = count[dc] + 1
if (i == pow - 1 || i == largest) {
var total = (dc == 1) ? 10 : pow * 0.9
var pc = 100 * count[dc] / total
Fmt.print(" $d digit colorful number count: $,6d - $7.3f\%", dc, count[dc], pc)
if (i == largest) break
dc = dc + 1
pow = pow * 10
i = pow * 0.2 + 2
} else {
i = i + 1
}
}
Fmt.print("\nTotal colorful numbers: $,d", Nums.sum(count))</lang>
- Output:
The colorful numbers less than 100 are: 0 1 2 3 4 5 6 7 8 9 23 24 25 26 27 28 29 32 34 35 36 37 38 39 42 43 45 46 47 48 49 52 53 54 56 57 58 59 62 63 64 65 67 68 69 72 73 74 75 76 78 79 82 83 84 85 86 87 89 92 93 94 95 96 97 98 The largest possible colorful number is: 98,746,253 Count of colorful numbers for each order of magnitude: 1 digit colorful number count: 10 - 100.000% 2 digit colorful number count: 56 - 62.222% 3 digit colorful number count: 328 - 36.444% 4 digit colorful number count: 1,540 - 17.111% 5 digit colorful number count: 5,514 - 6.127% 6 digit colorful number count: 13,956 - 1.551% 7 digit colorful number count: 21,596 - 0.240% 8 digit colorful number count: 14,256 - 0.016% Total colorful numbers: 57,256