Re: Array permutations
I also should discourage its current form with large `tupleSize`s. The computation is in O(exp(values.length)). Instead of `~=` I would suggest an `std.array.appender` of arrays instead of an 2D-array for the `choices`, if the `choices` become large. Most efficient is a preallocated array capacity. In that case `~=` has very low overhead.
Re: Array permutations
On Saturday, 11 September 2021 at 19:37:42 UTC, Vino wrote:
Hi All,
Request your help on the below to print the below array as
"Required output", Was able to get these values
"[1,2],[2,3],[3,4],[4,5]" by using list.slide(2), need your
help to get values "1,3],[1,4],[1,5],[2,4],[2,5],[3,5]"
auto list[] = [1,2,3,4,5]
Required output
[1,2],[2,3],[3,4],[4,5],[1,3],[1,4],[1,5],[2,4],[2,5],[3,5]
From,
Vino
Would this be a valid solution to your problem?
```D
pure @safe nothrow
T[][] computeChoices(T)(T[] values, size_t tupleSize = 2)
{
if (tupleSize == 0) {
return [[]];
}
T[][] choices = [];
tupleSize--;
foreach(i, element; values[0 .. $ - tupleSize])
{
import std.algorithm.iteration : map;
import std.array : array;
choices ~= computeChoices(values[i+1 .. $], tupleSize)
.map!(choice => element ~ choice)
.array;
}
return choices;
}
unittest
{
assert(computeChoices([1, 2, 3, 4, 5], 2)
== [[1,2], [1,3], [1,4], [1,5], [2,3], [2,4], [2,5],
[3,4], [3,5], [4,5]] );
}
```
You can choose in the 2nd parameter how large the inner arrays
should be. It uses GC to allocate the result via the function
`array`. If that is a problem, you could choose an allocator from
`std.experimental.allocator` and use the `makeArray` function
with the allocator instead of the `array` function. (Manual
deallocation could be required then as well.)
Re: Array permutations
On Saturday, 11 September 2021 at 23:04:29 UTC, Vino wrote: On Saturday, 11 September 2021 at 19:57:26 UTC, jfondren wrote: [...] Hi, Thank you very much, let me try to explain the actual requirement, the actual requirement is to find all the permutations of a given array, I modified your code and it gives me the exact output , but i need help to remove the array which has the same value as below [...] Hi, Was able to resolve the issue by adding the filter ".filter!"a[0] != a[1]" From, Vino
Re: Array permutations
On Saturday, 11 September 2021 at 19:57:26 UTC, jfondren wrote:
On Saturday, 11 September 2021 at 19:37:42 UTC, Vino wrote:
Hi All,
Request your help on the below to print the below array as
"Required output", Was able to get these values
"[1,2],[2,3],[3,4],[4,5]" by using list.slide(2), need your
help to get values "1,3],[1,4],[1,5],[2,4],[2,5],[3,5]"
auto list[] = [1,2,3,4,5]
Required output
[1,2],[2,3],[3,4],[4,5],[1,3],[1,4],[1,5],[2,4],[2,5],[3,5]
From,
Vino
I don't see the pattern just from the required output. If you
have an English description of what you want, it might be
easier.
Anyway, take a look at
```d
unittest {
import std.algorithm : cartesianProduct, filter, map, sort;
import std.range : drop;
import std.array : array;
auto list = [1,2,3,4,5];
auto required =
[[1,2],[2,3],[3,4],[4,5],[1,3],[1,4],[1,5],[2,4],[2,5],[3,5]];
auto pairs = list.cartesianProduct(list.drop(1))
.filter!"a[0] < a[1]"
.map!array
.array;
assert(pairs == [[1, 2], [1, 3], [1, 4], [1, 5], [2, 3],
[2, 4], [2, 5], [3, 4], [3, 5], [4, 5]]);
assert(required.sort.array == pairs);
}
```
Hi,
Thank you very much, let me try to explain the actual
requirement, the actual requirement is to find all the
permutations of a given array, I modified your code and it gives
me the exact output , but i need help to remove the array which
has the same value as below
Example:
void main() {
import std.algorithm : cartesianProduct, filter, map, sort;
import std.range : drop;
import std.array : array;
import std.stdio : writeln;
auto list = [1,2,3,4,5];
auto pairs = list.cartesianProduct(list)
.map!array
.array;
writeln(pairs);
}
Output
[
[1, 1], /* shodule not print this array */
[1, 2],
[1, 3],
[1, 4],
[1, 5],
[2, 1],
[2, 2], /* should not print this array */
[2, 3],
[2, 4],
[2, 5],
[3, 1],
[3, 2],
[3, 3], /* should not print this array */
[3, 4],
[3, 5],
[4, 1],
[4, 2],
[4, 3],
[4, 4], /* should not print this array */
[4, 5],
[5, 1],
[5, 2],
[5, 3],
[5, 4],
[5, 5] /* should not print this array */
]
From,
Vino
Re: Array permutations
On Saturday, 11 September 2021 at 19:57:26 UTC, jfondren wrote: auto pairs = list.cartesianProduct(list.drop(1)) This `drop` isn't necessary.
Re: Array permutations
On Saturday, 11 September 2021 at 19:37:42 UTC, Vino wrote:
Request your help on the below to print the below array as
"Required output", Was able to get these values
"[1,2],[2,3],[3,4],[4,5]" by using list.slide(2), need your
help to get values "1,3],[1,4],[1,5],[2,4],[2,5],[3,5]"
```d
import std;
auto slideEnds(List)(List list, size_t slideLen)
{ return list.slide(slideLen).map!(window => [window.front,
window.back]);
}
void main()
{ auto list = [1,2,3,4,5];
iota(2, list.length)
.map!(slideLen => list.slideEnds(slideLen))
.joiner
.writeln;
}
```
This almost does the trick. It leaves out `[1, 5]` for some
reason I didn't bother to check though.
Re: Array permutations
On Saturday, 11 September 2021 at 19:37:42 UTC, Vino wrote:
Hi All,
Request your help on the below to print the below array as
"Required output", Was able to get these values
"[1,2],[2,3],[3,4],[4,5]" by using list.slide(2), need your
help to get values "1,3],[1,4],[1,5],[2,4],[2,5],[3,5]"
auto list[] = [1,2,3,4,5]
Required output
[1,2],[2,3],[3,4],[4,5],[1,3],[1,4],[1,5],[2,4],[2,5],[3,5]
From,
Vino
I don't see the pattern just from the required output. If you
have an English description of what you want, it might be easier.
Anyway, take a look at
```d
unittest {
import std.algorithm : cartesianProduct, filter, map, sort;
import std.range : drop;
import std.array : array;
auto list = [1,2,3,4,5];
auto required =
[[1,2],[2,3],[3,4],[4,5],[1,3],[1,4],[1,5],[2,4],[2,5],[3,5]];
auto pairs = list.cartesianProduct(list.drop(1))
.filter!"a[0] < a[1]"
.map!array
.array;
assert(pairs == [[1, 2], [1, 3], [1, 4], [1, 5], [2, 3], [2,
4], [2, 5], [3, 4], [3, 5], [4, 5]]);
assert(required.sort.array == pairs);
}
```
Array permutations
Hi All, Request your help on the below to print the below array as "Required output", Was able to get these values "[1,2],[2,3],[3,4],[4,5]" by using list.slide(2), need your help to get values "1,3],[1,4],[1,5],[2,4],[2,5],[3,5]" auto list[] = [1,2,3,4,5] Required output [1,2],[2,3],[3,4],[4,5],[1,3],[1,4],[1,5],[2,4],[2,5],[3,5] From, Vino
