Create Permutations from Dictionary<string, List<string>>


A

Assimalyst

Hi

I have a Dictionary<string, List<string>>, which i have successfully
filled. My problem is I need to create a filter expression using all
possible permutations of its contents.

i.e. the dictionary essentially creates the following array:

Key Value

Column1 1
Column1 2
Column2 17

I want to then create an number of filter expressions:

Column1 = 1 AND Column2 = 17
Column1 = 2 AND Column2 = 17

I used a permutation library i found PermuteUtils (
http://www.koders.com/csharp/fid3768925A9A54C7E9E853737EE8E638B71457A936.aspx
) and the following code:

Dictionary<string, List<string>> distinctCellValues = new
Dictionary<string, List<string>>();
ArrayList queryClause = new ArrayList();

{
foreach (KeyValuePair<string, List<string>> kvp in
distinctCellValues)
{
foreach (string value in kvp.Value)
{
queryClause.Add(kvp.Key + " = " + value);
}
}

//Convert array to string array
string[] queryClauseString = queryClause.ToArray(typeof(string)) as
string[];

CreateFilterPermutations<string>(queryClauseString,
distinctCellValues.Count);
}

private void CreateFilterPermutations<T>(IEnumerable<T> input, int
count)
{
foreach (IEnumerable<T> permutation in
PermuteUtils.Permute<T>(input, count))
{
foreach (T i in permutation)
{
filterExpressions.Add(i);
}
}
}

This seems to work OK as far as running the CreateFilterPermutations
method, where i just cannot get it to do what i need.

I've manage to get myself very confused by all this, and this only
contains 2 columns. Potentially i could need to be generating
permutations of 10 columns/values or more!! I'm hoping someone can
straighten out my thoughts before my head explodes!!

Thanks
 
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F

Fred Mellender

There is a good chance I don't understand your problem, but here is my take:

I don't think you want the permutations of the array elements, but instead
want a subset of the Cartesian product of the array with itself. E.G. if
the array is A= [a, b, c], the Cartesian product A x A is
{(a,a), (a,b), (a,c), (b,a), (b,b), (b,c), (c,a), (c,b), (c,c)}. The subset
you want excludes an element whose coords are the same, and considers as
duplicates 2 elements that have the same coords (e.g. (a,b) and (b,a) are
the same).

So, you want {(a,b), (a,c), (b,co)}

If you only have a single array, X, crossed only once with itself,
containing more than one element, some potential pseudo code would be:

for (int i = 0; i < x.Length-1; i++)
{
for (int j = i+1; j < x.Length; j++)
{
myFilterList.Add(x.MyToString() + " AND " +
x[j].MyToString())
}
}

In your case, x is the list of KeyValue pairs from the dictionary, and you
need to convert each KeyValue to a string via MyToString(), so as to form a
filter, which you add to a list, myFilterList.

What I don't understand about your example:
You have the same key, Column1 associated with two different values. I
don't think the Dictionary allows this.


Assimalyst said:
Hi

I have a Dictionary<string, List<string>>, which i have successfully
filled. My problem is I need to create a filter expression using all
possible permutations of its contents.

i.e. the dictionary essentially creates the following array:

Key Value

Column1 1
Column1 2
Column2 17

I want to then create an number of filter expressions:

Column1 = 1 AND Column2 = 17
Column1 = 2 AND Column2 = 17

I used a permutation library i found PermuteUtils (
http://www.koders.com/csharp/fid3768925A9A54C7E9E853737EE8E638B71457A936.aspx
) and the following code:

Dictionary<string, List<string>> distinctCellValues = new
Dictionary<string, List<string>>();
ArrayList queryClause = new ArrayList();

{
foreach (KeyValuePair<string, List<string>> kvp in
distinctCellValues)
{
foreach (string value in kvp.Value)
{
queryClause.Add(kvp.Key + " = " + value);
}
}

//Convert array to string array
string[] queryClauseString = queryClause.ToArray(typeof(string)) as
string[];

CreateFilterPermutations<string>(queryClauseString,
distinctCellValues.Count);
}

private void CreateFilterPermutations<T>(IEnumerable<T> input, int
count)
{
foreach (IEnumerable<T> permutation in
PermuteUtils.Permute<T>(input, count))
{
foreach (T i in permutation)
{
filterExpressions.Add(i);
}
}
}

This seems to work OK as far as running the CreateFilterPermutations
method, where i just cannot get it to do what i need.

I've manage to get myself very confused by all this, and this only
contains 2 columns. Potentially i could need to be generating
permutations of 10 columns/values or more!! I'm hoping someone can
straighten out my thoughts before my head explodes!!

Thanks
 
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A

Assimalyst

Thank you Fred.

I think i had confused myself. Not sure I want permutations but rather
combinations.

Your code sample has given me some ideas that i think i can get
working with a bit of expansion.
I'll keep playing with it . . .

By the way, i think you understood my problem exactly. The bit you
didn't understand was just the way i represented it. I didn't have
duplicate keys it was more like

Column1 { 1, 2 }
Column2 { 17 }

Thanks again


There is a good chance I don't understand your problem, but here is my take:

I don't think you want the permutations of the array elements, but instead
want a subset of the Cartesian product of the array with itself. E.G. if
the array is A= [a, b, c], the Cartesian product A x A is
{(a,a), (a,b), (a,c), (b,a), (b,b), (b,c), (c,a), (c,b), (c,c)}. The subset
you want excludes an element whose coords are the same, and considers as
duplicates 2 elements that have the same coords (e.g. (a,b) and (b,a) are
the same).

So, you want {(a,b), (a,c), (b,co)}

If you only have a single array, X, crossed only once with itself,
containing more than one element, some potential pseudo code would be:

for (int i = 0; i < x.Length-1; i++)
{
for (int j = i+1; j < x.Length; j++)
{
myFilterList.Add(x.MyToString() + " AND " +
x[j].MyToString())
}

}

In your case, x is the list of KeyValue pairs from the dictionary, and you
need to convert each KeyValue to a string via MyToString(), so as to form a
filter, which you add to a list, myFilterList.

What I don't understand about your example:
You have the same key, Column1 associated with two different values. I
don't think the Dictionary allows this.


I have a Dictionary<string, List<string>>, which i have successfully
filled. My problem is I need to create a filter expression using all
possible permutations of its contents.
i.e. the dictionary essentially creates the following array:
Key Value
Column1 1
Column1 2
Column2 17
I want to then create an number of filter expressions:
Column1 = 1 AND Column2 = 17
Column1 = 2 AND Column2 = 17
I used a permutation library i found PermuteUtils (
http://www.koders.com/csharp/fid3768925A9A54C7E9E853737EE8E638B71457A...
) and the following code:
Dictionary<string, List<string>> distinctCellValues = new
Dictionary<string, List<string>>();
ArrayList queryClause = new ArrayList();
{
foreach (KeyValuePair<string, List<string>> kvp in
distinctCellValues)
{
foreach (string value in kvp.Value)
{
queryClause.Add(kvp.Key + " = " + value);
}
}
//Convert array to string array
string[] queryClauseString = queryClause.ToArray(typeof(string)) as
string[];
CreateFilterPermutations<string>(queryClauseString,
distinctCellValues.Count);
}

private void CreateFilterPermutations<T>(IEnumerable<T> input, int
count)
{
foreach (IEnumerable<T> permutation in
PermuteUtils.Permute<T>(input, count))
{
foreach (T i in permutation)
{
filterExpressions.Add(i);
}
}
}
This seems to work OK as far as running the CreateFilterPermutations
method, where i just cannot get it to do what i need.
I've manage to get myself very confused by all this, and this only
contains 2 columns. Potentially i could need to be generating
permutations of 10 columns/values or more!! I'm hoping someone can
straighten out my thoughts before my head explodes!!
 

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