On Friday, 27 January 2017 at 05:48:27 UTC, Stefan Koch wrote:
To me it looks rather slow.
please benchmark!
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;
}
resulted in:
TickDuration(28085)
TickDuration(42868)
TickDuration(1509)
So, you were correct that the original method is better than
Wilsons filter. My method is much better for large arrays I
tested here. But what I think you were afraid of is that it
needlessly wastes performance by allocating a new array, and I
agree.
Also, as I said, it could be made O(n).
