Strange plus numbers: Difference between revisions
Catskill549 (talk | contribs) |
|||
Line 236: | Line 236: | ||
389 411 412 414 416 430 432 434 438 470 |
389 411 412 414 416 430 432 434 438 470 |
||
474 476 492 494 498</pre> |
474 476 492 494 498</pre> |
||
=={{header|AWK}}== |
|||
<lang AWK> |
|||
# syntax: GAWK -f STRANGE_PLUS_NUMBERS.AWK |
|||
BEGIN { |
|||
start = 100 |
|||
stop = 500 |
|||
for (i=start; i<=stop; i++) { |
|||
c1 = substr(i,1,1) |
|||
c2 = substr(i,2,1) |
|||
c3 = substr(i,3,1) |
|||
if (is_prime(c1 + c2) && is_prime(c2 + c3)) { |
|||
printf("%d%1s",i,++count%10?"":"\n") |
|||
} |
|||
} |
|||
printf("\nStrange plus numbers %d-%d: %d\n",start,stop,count) |
|||
exit(0) |
|||
} |
|||
function is_prime(x, i) { |
|||
if (x <= 1) { |
|||
return(0) |
|||
} |
|||
for (i=2; i<=int(sqrt(x)); i++) { |
|||
if (x % i == 0) { |
|||
return(0) |
|||
} |
|||
} |
|||
return(1) |
|||
} |
|||
</lang> |
|||
{{out}} |
|||
<pre> |
|||
111 112 114 116 120 121 123 125 129 141 |
|||
143 147 149 161 165 167 202 203 205 207 |
|||
211 212 214 216 230 232 234 238 250 252 |
|||
256 258 292 294 298 302 303 305 307 320 |
|||
321 323 325 329 341 343 347 349 383 385 |
|||
389 411 412 414 416 430 432 434 438 470 |
|||
474 476 492 494 498 |
|||
Strange plus numbers 100-500: 65 |
|||
</pre> |
|||
=={{header|C}}== |
=={{header|C}}== |
Revision as of 18:22, 19 March 2021
n is a strange plus number if the sum of the first two digits is prime and the sum of the second two digits is also prime.
Where 100 < n < 500
- Related task
APL
<lang APL>(∧⌿ 2 3 5 7 11 13 17 ∊⍨ 2 +⌿ 10 (⊥⍣¯1) X)/X←100+⍳399</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
AppleScript
<lang applescript>------------------- STRANGE PLUS NUMBERS -----------------
-- isStrangePlus :: Int -> Bool on isStrangePlus(n)
set ds to digits(n) script sumIsSmallPrime on |λ|(a, b) {2, 3, 5, 7, 11, 13, 17} contains (a + b) end |λ| end script zipWith(sumIsSmallPrime, ds, rest of ds) does not contain false
end isStrangePlus
TEST -------------------------
on run
set xs to filter(isStrangePlus, enumFromTo(100, 500)) intercalate("\n\n", ¬ {"'Strange Plus' numbers found in range [100..500]", ¬ "Full list:", ¬ ("(total " & (length of xs) as string) & ")", ¬ unlines(map(unwords, chunksOf(10, map(str, xs))))})
end run
GENERIC ------------------------
-- chunksOf :: Int -> [a] -> a on chunksOf(k, xs)
script on go(ys) set ab to splitAt(k, ys) set a to item 1 of ab if {} ≠ a then {a} & go(item 2 of ab) else a end if end go end script result's go(xs)
end chunksOf
-- digits :: Int -> [Int]
on digits(n)
script go on |λ|(x) x as integer end |λ| end script map(go, characters of (n as string))
end digits
-- enumFromTo :: Int -> Int -> [Int]
on enumFromTo(m, n)
if m ≤ n then set lst to {} repeat with i from m to n set end of lst to i end repeat lst else {} end if
end enumFromTo
-- intercalate :: String -> [String] -> String
on intercalate(delim, xs)
set {dlm, my text item delimiters} to ¬ {my text item delimiters, delim} set s to xs as text set my text item delimiters to dlm s
end intercalate
-- filter :: (a -> Bool) -> [a] -> [a]
on filter(p, xs)
tell mReturn(p) set lst to {} set lng to length of xs repeat with i from 1 to lng set v to item i of xs if |λ|(v, i, xs) then set end of lst to v end repeat if {text, string} contains class of xs then lst as text else lst end if end tell
end filter
-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
-- 2nd class handler function lifted into 1st class script wrapper. if script is class of f then f else script property |λ| : f end script end if
end mReturn
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
-- The list obtained by applying f -- to each element of xs. tell mReturn(f) set lng to length of xs set lst to {} repeat with i from 1 to lng set end of lst to |λ|(item i of xs, i, xs) end repeat return lst end tell
end map
-- min :: Ord a => a -> a -> a
on min(x, y)
if y < x then y else x end if
end min
-- splitAt :: Int -> [a] -> ([a], [a])
on splitAt(n, xs)
if n > 0 and n < length of xs then if class of xs is text then {items 1 thru n of xs as text, ¬ items (n + 1) thru -1 of xs as text} else {items 1 thru n of xs, items (n + 1) thru -1 of xs} end if else if n < 1 then {{}, xs} else {xs, {}} end if end if
end splitAt
-- str :: a -> String
on str(x)
x as string
end str
-- unlines :: [String] -> String
on unlines(xs)
-- A single string formed by the intercalation -- of a list of strings with the newline character. set {dlm, my text item delimiters} to ¬ {my text item delimiters, linefeed} set s to xs as text set my text item delimiters to dlm s
end unlines
-- unwords :: [String] -> String
on unwords(xs)
set {dlm, my text item delimiters} to ¬ {my text item delimiters, space} set s to xs as text set my text item delimiters to dlm return s
end unwords
-- zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
on zipWith(f, xs, ys)
set lng to min(length of xs, length of ys) set lst to {} if 1 > lng then return {} else tell mReturn(f) repeat with i from 1 to lng set end of lst to |λ|(item i of xs, item i of ys) end repeat return lst end tell end if
end zipWith</lang>
- Output:
'Strange Plus' numbers found in range [100..500] Full list: (total 65) 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
AWK
<lang AWK>
- syntax: GAWK -f STRANGE_PLUS_NUMBERS.AWK
BEGIN {
start = 100 stop = 500 for (i=start; i<=stop; i++) { c1 = substr(i,1,1) c2 = substr(i,2,1) c3 = substr(i,3,1) if (is_prime(c1 + c2) && is_prime(c2 + c3)) { printf("%d%1s",i,++count%10?"":"\n") } } printf("\nStrange plus numbers %d-%d: %d\n",start,stop,count) exit(0)
} function is_prime(x, i) {
if (x <= 1) { return(0) } for (i=2; i<=int(sqrt(x)); i++) { if (x % i == 0) { return(0) } } return(1)
} </lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498 Strange plus numbers 100-500: 65
C
Generalized solution: a number is strange iff the sum of two consecutive digits is always prime. Numbers < 10 are considered non-strange.
<lang c>#include <stdio.h>
static int p[19] = {0, 0, 1, 1, 0, 1, 0, 1, 0, 0,
0, 1, 0, 1, 0, 0, 0, 1, 0};
int isstrange(long n) {
if (n < 10) return 0; for (; n >= 10; n /= 10) { if (!p[n%10 + (n/10)%10]) return 0; } return 1;
}
int main(void) {
long n; int k = 0;
for (n = 101; n < 500; n++) { if (isstrange(n)) { printf("%d%c", n, ++k%10 ? ' ' : '\n'); } } return 0;
}</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
F#
This task uses Extensible Prime Generator (F#).
<lang fsharp>
// Strange numbers. Nigel Galloway: February 25th., 2021
let pD=[0..99]|>List.map(fun n->(n/10,n%10))|>List.filter(fun(n,g)->isPrime(n+g))
pD|>List.filter(fun(n,_)->n>0)|>List.map(fun(n,g)->(n,pD|>List.filter(fun(n,_)->n=g)))
|>List.collect(fun(n,g)->g|>List.map(fun(g,k)->n*100+g*10+k))|>List.filter((>)500)|>List.iter(printf "%d ");printfn ""
</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Factor
<lang factor>USING: grouping grouping.extras io kernel math math.primes math.ranges math.text.utils prettyprint sequences ;
- strange+? ( n -- ? )
dup 10 < [ drop f ] [ 1 digit-groups [ + ] 2 clump-map [ prime? ] all? ] if ;
"Strange plus numbers in (100, 500):" print nl 100 500 (a,b) [ strange+? ] filter dup 10 group [ [ pprint bl ] each nl ] each nl length pprint " strange plus numbers found." print</lang>
- Output:
Strange plus numbers in (100, 500): 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498 65 strange plus numbers found.
Forth
<lang forth>create isprime false , false , true , true , false ,
true , false , true , false , false , false , true , false , true , false , false , false , true , false ,
\ tests whether n is prime for 0 <= n < 19
- prime? ( n -- ? )
cells isprime + @ ;
- strange? ( n -- ? )
dup 10 < if drop false exit then begin dup 10 >= while dup 10 /mod 10 mod + prime? invert if drop false exit then 10 / repeat drop true ;
- main
0 500 101 do i strange? if i . 1+ dup 10 mod 0= if cr then else then loop cr drop ;
main bye</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Go
<lang go>package main
import "fmt"
func isPrime(n int) bool {
return n == 2 || n == 3 || n == 5 || n == 7 || n == 11 || n == 13 || n == 17
}
func main() {
count := 0 var d []int fmt.Println("Strange plus numbers in the open interval (100, 500) are:\n") for i := 101; i < 500; i++ { d = d[:0] j := i for j > 0 { d = append(d, j%10) j /= 10 } if isPrime(d[0]+d[1]) && isPrime(d[1]+d[2]) { fmt.Printf("%d ", i) count++ if count%10 == 0 { fmt.Println() } } } if count%10 != 0 { fmt.Println() } fmt.Printf("\n%d strange plus numbers in all.\n", count)
}</lang>
- Output:
Strange plus numbers in the open interval (100, 500) are: 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498 65 strange plus numbers in all.
Haskell
<lang haskell>import Data.List (intercalate) import Data.List.Split (chunksOf)
STRANGE PLUS NUMBERS -----------------
isStrangePlus :: Int -> Bool isStrangePlus n =
all (\(a, b) -> (a + b) `elem` [2, 3, 5, 7, 11, 13, 17]) $ (zip <*> tail) (digits n)
digits :: Int -> [Int]
digits = fmap (read . return) . show
TEST -------------------------
main =
let xs = filter isStrangePlus [100 .. 500] in (putStrLn . intercalate "\n\n") [ "\"Strange Plus\" numbers found in range [100..500]", "(total " <> (show . length) xs <> ")", "Full list:", unlines (unwords <$> chunksOf 10 (show <$> xs)) ]</lang>
- Output:
"Strange Plus" numbers found in range [100..500] (total 65) Full list: 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Java
<lang java>public class Strange {
private static final boolean[] p = { false, false, true, true, false, true, false, true, false, false, false, true, false, true, false, false, false, true, false };
public static boolean isstrange(long n) { if (n < 10) return false; for (; n >= 10; n /= 10) { if (!p[(int)(n%10 + (n/10)%10)]) return false; } return true; }
public static void main(String[] args) { long nMin = Long.parseLong(args[0]); long nMax = Long.parseLong(args[1]); int k = 0; for (long n = nMin; n <= nMax; n++) { if (isstrange(n)) { System.out.print(n + (++k%10 != 0 ? " " : "\n")); } } }
}</lang>
<lang>java Strange 101 499</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Julia
<lang julia>let
smallprimes = [2, 3, 5, 7, 11, 13, 17] # 0 <= all of these primes <= 18 paired_digit_sums(n) = (d = digits(n); [sum(p) for p in zip(d[1:end-1], d[2:end])]) isstrangeplus(n) = all(x -> x ∈ smallprimes, paired_digit_sums(n)) printed = 0 for n in 100:500 isstrangeplus(n) && print(n, (printed += 1) % 13 == 0 ? "\n" : " ") end
end
</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Kotlin
<lang scala>val p = arrayOf(
false, false, true, true, false, true, false, true, false, false, false, true, false, true, false, false, false, true, false
)
fun isStrange(n: Long): Boolean {
if (n < 10) { return false }
var nn = n while (nn >= 10) { if (!p[(nn % 10 + (nn / 10) % 10).toInt()]) { return false } nn /= 10 }
return true
}
fun test(nMin: Long, nMax: Long) {
var k = 0 for (n in nMin..nMax) { if (isStrange(n)) { print(n) if (++k % 10 != 0) { print(' ') } else { println() } } }
}
fun main() {
test(101, 499)
}</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Maple
<lang maple>select(n->(u->isprime(add(u[1..2])) and isprime(add(u[2..3])))(convert(n,base,10)),[$101..499]);</lang>
- Output:
[111, 112, 114, 116, 120, 121, 123, 125, 129, 141, 143, 147, 149, 161, 165, 167, 202, 203, 205, 207, 211, 212, 214, 216, 230, 232, 234, 238, 250, 252, 256, 258, 292, 294, 298, 302, 303, 305, 307, 320, 321, 323, 325, 329, 341, 343, 347, 349, 383, 385, 389, 411, 412, 414, 416, 430, 432, 434, 438, 470, 474, 476, 492, 494, 498]
Perl
<lang perl>use strict; use warnings; use feature 'say'; use ntheory 'is_prime';
my($low, $high) = (100, 500); my $n = my @SP = grep { my @d = split ; is_prime $d[0]+$d[1] and is_prime $d[1]+$d[2] } $low+1 .. $high-1; say "Between $low and $high there are $n strange-plus numbers:\n" .
(sprintf "@{['%4d' x $n]}", @SP[0..$n-1]) =~ s/(.{80})/$1\n/gr;</lang>
- Output:
Between 100 and 500 there are 65 strange-plus numbers: 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Phix
Using the same approach as Strange_numbers#Phix, so this should similarly scale/count easily to the 28-digit range. <lang Phix>constant poss = apply(true,sq_sub,{{get_primes(-7)},tagset(9,0)}),
nxts = apply(true,filter,{poss,{"in"},Template:0,9,{"[]"}})
function strange_plus(integer left, sequence digits, res={}, part={})
for i=1 to length(digits) do integer di = digits[i] if left=1 then string fmt = join(repeat("%d",length(part)+1),"") res = append(res,sprintf(fmt,part&di)) else res = strange_plus(left-1,nxts[di+1],res,part&di) end if end for return res
end function
sequence res = strange_plus(3,tagset(4)) -- (3 digit numbers beginning 1..4) printf(1,"%d strange_plus numbers found: %s\n",{length(res),join(shorten(res,"",5),",")})</lang>
- Output:
65 strange_plus numbers found: 111,112,114,116,120,...,474,476,492,494,498
Python
Using sympy.isprime
<lang python>Python 3.8.5 (default, Sep 3 2020, 21:29:08) [MSC v.1916 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license()" for more information. >>> from sympy import isprime
>>> [x for x in range(101,500)
if isprime(sum(int(c) for c in str(x)[:2])) and isprime(sum(int(c) for c in str(x)[1:]))]
[111, 112, 114, 116, 120, 121, 123, 125, 129, 141, 143, 147, 149, 161, 165, 167, 202, 203, 205, 207, 211, 212, 214, 216, 230, 232, 234, 238, 250, 252, 256, 258, 292, 294, 298, 302, 303, 305, 307, 320, 321, 323, 325, 329, 341, 343, 347, 349, 383, 385, 389, 411, 412, 414, 416, 430, 432, 434, 438, 470, 474, 476, 492, 494, 498] >>> </lang>
Or, as we may not need to wake up sympy just to check membership of {2, 3, 5, 7, 11, 13, 17}:
<lang python>Strange Plus Numbers
- isStrangePlus :: Int -> Bool
def isStrangePlus(n):
True all consecutive decimal digit pairs in n have prime sums. def test(a, b): return a + b in [2, 3, 5, 7, 11, 13, 17]
xs = digits(n) return all(map(test, xs, xs[1:]))
- ------------------- TEST AND DISPLAY -------------------
- main :: IO ()
def main():
List and count of Strange Plus Numbers
xs = [ n for n in range(100, 1 + 500) if isStrangePlus(n) ] print('\n"Strange Plus" numbers in range [100..500]\n') print('(Total: ' + str(len(xs)) + ')\n') print( '\n'.join( ' '.join( str(x) for x in row ) for row in chunksOf(10)(xs) ) )
- ----------------------- GENERIC ------------------------
- chunksOf :: Int -> [a] -> a
def chunksOf(n):
A series of lists of length n, subdividing the contents of xs. Where the length of xs is not evenly divible, the final list will be shorter than n. def go(xs): return ( xs[i:n + i] for i in range(0, len(xs), n) ) if 0 < n else None return go
- digits :: Int -> [Int]
def digits(n):
Component digits of a decimal number. return [int(c) for c in str(n)]
- MAIN ---
if __name__ == '__main__':
main()</lang>
- Output:
"Strange Plus" numbers in range [100..500] (Total: 65) 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Raku
<lang perl6>unit sub MAIN ($start = 100, $end = 500); put +$_, " matching numbers from $start to $end:\n", $_ given
($start .. $end).hyper(:256batch,:8degree).grep: { all .comb.rotor(2 => -1).map: { .sum.is-prime } };</lang>
- Output:
65 matching numbers from 100 to 500: 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
REXX
<lang rexx>/*REXX pgm lists strange+ integers (within a range); sum of adjacent dec. digs is prime.*/ parse arg LO HI . /*obtain optional arguments from the CL*/ if LO== | LO=="," then LO= 101 /*Not specified? Then use the default.*/ if HI== | HI=="," then HI= 499 /* " " " " " " */ !.= 0; !.2= 1; !.3= 1; !.5= 1; !.7= 1 /*build array of sums that are prime. */
!.11= 1; !.13= 1; !.17= 1 /* " " " " " " " */
$= /*the list of strange+ numbers (so far)*/
- = 0 /* " number " " " " " */
do j=LO to HI; L= length(j) /*look for strange+ numbers in range. */ if L==1 then iterate /*Number too short? Then skip it. */
do k=1 for L-1 /*examine the difference in the digits.*/ parse var j =(k) y +1 z +1 /*get two adjacent decimal digits: Y Z */ sum= y + z /*sum of two adjacent decimal digits. */ if \!.sum then iterate j /*Sum not prime? Then skip this number*/ end /*k*/ #= # + 1 /*bump the number of "strange+" numbers*/ $= $ j /*append the number to the $ list. */ end /*j*/ /*stick a fork in it, we're all done. */
say # ' strange plus numbers found between ' LO " and " HI ' (inclusive)' say say strip($)</lang>
- output when using the default inputs:
65 strange plus numbers found between 101 and 499 (inclusive) 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Ring
<lang ring> load "stdlib.ring"
row = 0 see "Strange plus numbers are:" + nl
for n = 100 to 500
flag = 1 str = string(n) for m = 1 to len(str)-1 num1 = number(str[m]) num2 = number(str[m+1]) pr = num1+num2 if not isprime(pr) flag = 0 exit ok next if flag = 1 see str + " " row = row + 1 if row % 10 = 0 see nl ok ok
next </lang>
- Output:
Strange plus numbers are: 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Ruby
<lang ruby>$p = [
false, false, true, true, false, true, false, true, false, false, false, true, false, true, false, false, false, true, false
]
def isStrange(n)
if n < 10 then return false end
while n >= 10 do if not $p[n % 10 + (n / 10).floor % 10] then return false end n = (n / 10).floor end
return true
end
def test(nMin, nMax)
k = 0 for n in nMin .. nMax if isStrange(n) then print n k = k + 1 if k % 10 != 0 then print ' ' else print "\n" end end end
end
test(101, 499)</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498
Wren
Simple brute force is adequate for this. <lang ecmascript>var primes = [2, 3, 5, 7, 11, 13, 17] var count = 0 var d = [] System.print("Strange plus numbers in the open interval (100, 500) are:\n") for (i in 101..499) {
d.clear() var j = i while (j > 0) { d.add(j % 10) j = (j/10).floor } if (primes.contains(d[0] + d[1]) && primes.contains(d[1] + d[2])) { System.write("%(i) ") count = count + 1 if (count % 10 == 0) System.print() }
} if (count % 10 != 0) System.print() System.print("\n%(count) strange plus numbers in all.")</lang>
- Output:
Strange plus numbers in the open interval (100, 500) are: 111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498 65 strange plus numbers in all.
x86 Assembly
A 16-bit solution for NASM under DOS. Assemble with nasm -fbin strange.asm -o strange.com
. The prime sieve up to 18 is hard-coded.
<lang> org 100h
mov cx, 10 ; cl is used for division, ch to count numbers printed on a line mov si, 101 ; loop index from 101 to 499 mov di, p ; pointer to prime sieve ; p+k is a pointer to the reversed string repr. of the current index
L1 mov ax, si
xor bx, bx ; bx counts characters in the string
L2 div cl ; div by 10 to get last digit
add ah, 48 ; convert digit to ascii mov [bx+di+k], ah ; store char test bl, bl ; if it's the first, don't check for prime sum jz L3 add ah, [bx+di+k-1] ; sum of digits sub ah, 96 ; adjust for ascii xchg ah, bl cmp byte [bx+di], 1 ; is it prime? jne L6 ; otherwise continue with next number mov bl, ah ; restore bl
L3 xor ah, ah ; must be zero for the next division
inc bx ; one more char test al, al ; are there more digits? jnz L2
L4 mov ah, 2 ; the number is strange, print it char by char
mov dl, [bx+di+k-1] int 21h dec bx jnz L4 mov ah, 2 ; print a space or a newline mov dl, 32 inc ch cmp ch, 10 ; if less than 10 on the current line it's a space jne L5 mov dl, 10 ; otherwise it's a newline xor ch, ch ; reset the counter when we reach 10
L5 int 21h
L6 inc si ; next number
cmp si, 500 ; and loop until we reach 500 jb L1 int 20h ; return to DOS
p db 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0 k equ $-p</lang>
- Output:
111 112 114 116 120 121 123 125 129 141 143 147 149 161 165 167 202 203 205 207 211 212 214 216 230 232 234 238 250 252 256 258 292 294 298 302 303 305 307 320 321 323 325 329 341 343 347 349 383 385 389 411 412 414 416 430 432 434 438 470 474 476 492 494 498