D idom for removing array elements
cym13 via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Sat Jan 28 03:54:58 PST 2017
On Saturday, 28 January 2017 at 10:46:29 UTC, albert-j wrote:
> On Friday, 27 January 2017 at 08:15:56 UTC, Dukc wrote:
>
>> void main()
>> { import std.stdio, std.algorithm, std.range, std.array,
>> std.datetime;
>> int[] a = [1, 2, 3, 4, 5, 6, 7, 4].cycle.take(2000).array;
>> int[] b = [3, 4, 6].cycle.take(2000).array;
>>
>> void originalMethod()
>> { auto c = a.remove!(x => b.canFind(x));
>> assert(c[0 .. 4] == [1, 2, 5, 7]);
>> }
>>
>> void WilsonMethod()
>> { auto c = a.filter!(x => !b.canFind(x)).array;
>> assert(c[0 .. 4] == [1, 2, 5, 7]);
>> }
>>
>> void myMethod()
>> { auto sortedB = sort(b.dup);
>> auto c = a
>> . filter!(i => !sortedB.contains(i))
>> . array
>> ;
>> assert(c[0 .. 4] == [1, 2, 5, 7]);
>> }
>>
>> auto r = benchmark!(originalMethod, WilsonMethod,
>> myMethod)(1);
>> foreach(result; r) result.writeln;
>> }
>
>
> How to make it work with std.container.array?
Here is an example:
import std.container.array;
alias ArrI = Array!int;
auto removeAll(ArrI a, ArrI b) {
import std.array;
import std.range;
import std.algorithm;
auto sortedB = sort(b[]).uniq.array;
auto c = a[].partition!(v => sortedB.assumeSorted.contains(v),
SwapStrategy.stable);
return ArrI(c);
}
void main() {
import std.stdio;
auto a = ArrI(1, 2, 3, 4, 5, 6, 7, 4);
auto b = ArrI(3, 4, 6);
a.removeAll(b)[].writeln;
}
Note especially how you slice an Array to access its data.
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