CODEWITHSUNDEEP
stringalgorithm
Ari
Ari

Reputation: 3086

Generating all Possible Combinations of a Sentence with Variables

Say I have a sentence with multiple variables as follows:

"lorem ipsum {a, b} dolor {c, d, e} sit amet"

Assuming the letters in the braces are variables, how would one go about generating a group of sentences out of all possible combinations of the variables?

Note: The number of variable groups or variable count within each group of variables is unknown.

The expected output for this particular example would be:

"lorem ipsum {a} dolor {c} sit amet"
"lorem ipsum {b} dolor {c} sit amet"
"lorem ipsum {a} dolor {d} sit amet"
"lorem ipsum {b} dolor {d} sit amet"
"lorem ipsum {a} dolor {e} sit amet"
"lorem ipsum {b} dolor {e} sit amet"

Upvotes: 3

Views: 253

Answers (2)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186813

In general case ("number of variable groups... count within each group ... is unknown") we should parse the initial string (let's do it with a help of regular expressions) and then enumerate all the combinations.

C# Code:

using System.Text.RegularExpressions;
...

private static IEnumerable<string> Generator(string source) {
  // parsing: variables extracted: array of variables and their possible values
  string[][] variables = Regex
    .Matches(source, @"\{.*?\}")
    .OfType<Match>()
    .Select(match => match
       .Value
       .Trim('{', '}')
       .Split(',')
       .Select(item => "{" + item.Trim() + "}")
       .ToArray())
    .ToArray();

  // now we should enumerate all possible variables' values
  int[] indexes = new int[variables.Length];

  do {
    // code golf : ugly side effects but short code
    int at = 0;

    yield return Regex.Replace(source, @"\{.*?\}", match => variables[at][indexes[at++]]);

    for (int i = 0; i < indexes.Length; ++i)
      if (indexes[i] < variables[i].Length - 1) {
        indexes[i] = indexes[i] + 1;

        break;
      }
      else
        indexes[i] = 0;
  }
  while (!indexes.All(index => index == 0));
}

Demo:

string source = @"lorem ipsum {a, b} dolor {c, d, e} sit amet";

string report = string.Join(Environment.NewLine, Generator(source));

Console.Write(report);

Outcome:

lorem ipsum {a} dolor {c} sit amet
lorem ipsum {b} dolor {c} sit amet
lorem ipsum {a} dolor {d} sit amet
lorem ipsum {b} dolor {d} sit amet
lorem ipsum {a} dolor {e} sit amet
lorem ipsum {b} dolor {e} sit amet

Another example:

// 3 groups of variables with strange names
string source = @"lorem ipsum {A + 2, B, C?} dolor {XY, PQR} sit {eh?, bla-bla-bla} amet";

Console.Write(string.Join(Environment.NewLine, Generator(source)));

Outcome:

lorem ipsum {A + 2} dolor {XY} sit {eh?} amet
lorem ipsum {B} dolor {XY} sit {eh?} amet
lorem ipsum {C?} dolor {XY} sit {eh?} amet
lorem ipsum {A + 2} dolor {PQR} sit {eh?} amet
lorem ipsum {B} dolor {PQR} sit {eh?} amet
lorem ipsum {C?} dolor {PQR} sit {eh?} amet
lorem ipsum {A + 2} dolor {XY} sit {bla-bla-bla} amet
lorem ipsum {B} dolor {XY} sit {bla-bla-bla} amet
lorem ipsum {C?} dolor {XY} sit {bla-bla-bla} amet
lorem ipsum {A + 2} dolor {PQR} sit {bla-bla-bla} amet
lorem ipsum {B} dolor {PQR} sit {bla-bla-bla} amet
lorem ipsum {C?} dolor {PQR} sit {bla-bla-bla} amet

Upvotes: 2

Zohar Peled
Zohar Peled

Reputation: 82514

So basically you want to iterate two different arrays for all possible combinations of a single value from each array - Nested loops is probably the best option.

Here's a c# code to do that, with comments on each line for easy translation to other languages:

var values0 = new string[] {"a", "b"}; // All possible values for first slot
var values1 = new string[] {"c", "d", "e"}; // All possible values for second slot

foreach(var val0 in values0) // Iterate first array
{
    foreach(var val1 in values1) // Iterate second array
    {
        var result = $"Lorem ipsum {val0} dolor {val1} sit amet"; // Insert values to slots
        Console.WriteLine(str); // output
    }
}

Result:

Lorem ipsum a dolor c sit amet
Lorem ipsum a dolor d sit amet
Lorem ipsum a dolor e sit amet
Lorem ipsum b dolor c sit amet
Lorem ipsum b dolor d sit amet
Lorem ipsum b dolor e sit amet

Upvotes: 1

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