C# to D

Dennis Ritchie via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Wed Mar 25 15:00:04 PDT 2015


On Wednesday, 25 March 2015 at 20:09:53 UTC, bearophile wrote:
> This is still not very efficient (perhaps the last sorting has 
> to be stable):
>
> void main() {
>     import std.stdio, std.algorithm, std.typecons, std.array;
>
>     [7, 5, 7, 3, 3, 5, 3, 3, 0, 3, 1, 1, 5, 1, 1, 1, 2, 2, 8, 
> 5, 8, 8]
>     .sort()
>     .groupBy!((a, b) => a == b)
>     .map!array
>     .array
>     .sort!q{a.length > b.length}
>     .joiner
>     .writeln;
> }

On Wednesday, 25 March 2015 at 20:53:43 UTC, Ivan Kazmenko wrote:
> 5. An efficient version would be to count the integers by using 
> an associative array (or a redBlackTree for guaranteed upper 
> bound) and then use these.  It is O (n) time and memory spent 
> in precalculation phase and O (n log n) time for sorting.  
> Looks like there is no way to write that as a chain of 
> transforms, but many optimizations do require manual labor.
>
> -----
> import std.algorithm, std.conv, std.range, std.stdio;
> void main () {
>     auto arr = [7, 5, 7, 3, 3, 5, 3, 3, 0, 3, 1, 1, 5, 1,
> 1, 1, 2, 2, 8, 5, 8, 8];
>     int [int] counts;
>     foreach (e; arr) {
>         counts[e]++;
>     }
>     arr.multiSort !((a, b) => counts[a] > counts[b], (a, b) => 
> a < b);
>     arr.map !(to !(string))
>         .join (" ")
>         .writeln;
>     // prints 1 1 1 1 1 3 3 3 3 3 5 5 5 5 8 8 8 2 2 7 7 0
> }
> -----

Thank you very much, Ivan and bearophile!

On Wednesday, 25 March 2015 at 20:53:43 UTC, Ivan Kazmenko wrote:
> Also, some of my previously posted codes do not compile under 
> 2.066 or earlier unless you replace .join (' ') with .join (" 
> ") there.

I have long been updated :)


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