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Re: Number-Theory :: All-Digit Perfect Squares
*To*: mathgroup at smc.vnet.net
*Subject*: [mg64271] Re: [mg64264] Number-Theory :: All-Digit Perfect Squares
*From*: Bob Hanlon <hanlonr at cox.net>
*Date*: Thu, 9 Feb 2006 02:44:37 -0500 (EST)
*Reply-to*: hanlonr at cox.net
*Sender*: owner-wri-mathgroup at wolfram.com
test[x_]:=And@@(MemberQ[IntegerDigits[x],#]&/@Range[9]);
Select[Range[11111,31427]^2,test[#]&]
Bob Hanlon
>
> From: bd satish <bdsatish at gmail.com>
To: mathgroup at smc.vnet.net
> Subject: [mg64271] [mg64264] Number-Theory :: All-Digit Perfect Squares
>
> Hi buddies,
>
>
> I set out to write a code that generates nine-digit
> perfect square numbers , with each of the digits 1,2,3,...9 occuring only
once
> in a given number. An example is 139854276 = 11826^2 . Obviuously ,
all
> such numbers must lie in the interval [123456789 , 987654321] . Since
> 11111^2 < 123456789 and 31427^2 > 987654321 , all the square
numbers must
> have their square-roots
> in the interval (11111,31427) .
>
> I need suggetions from you guys to help me improve the code or
> to make it better or
> shorter.
>
> The logic I used is this:
>
> (a). Generate all the squares of integers in the range [11111,31427]
>
> (b). Seperate the numbers into digits (using the command IntegerDigits[ ]
> )
>
> (c). Check , how many (or which and all) numbers in this list have each
> of the digits 1,2,3,...8,9 exactly once.
>
> (d). Collect all those lists and put them back as numbers (using the
> command FromDigits[ ] )
>
>
> Here is the actual code:
>
> squares = IntegerDigits[Table[i ^ 2 , { i,11111,31427}]];
> sel = { } ; (* empty-list*)
> Do[
> p = squares[[k]];
> logic =
> And[MemberQ[p,1],MemberQ[p,2],MemberQ[p,3],MemberQ[p,4],MemberQ
[p,5],MemberQ[p,6],
> MemberQ[p,7],MemberQ[p,8],MemberQ[p,9] ] ;
>
> If[TrueQ[logic] , sel = Append[sel,p]] ,
> {k,1,Length[squares]}
> ];
> Map[FromDigits,sel,{1}]
>
> The code does work perfectly, giving a list of 30 such numbers.
>
> Will anyone help to to improve the code , if possible ?
>
> I would like to get rid of MemberQ[..] repeated so often.
>
>
>
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