iterate through the possible anagrams of a given string and use the result to create a regular expression in csharp

main.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

class MainClass {
  public static void Main (string[] args) {
    string input = "abc";

    // Find all the permutations of the input string
    List<string> permutations = GetPermutations(input);

    // Join the permutations into a regular expression pattern
    string pattern = String.Join("|", permutations);

    // Use the pattern to match against other strings
    string testString = "bca";
    if (Regex.IsMatch(testString, pattern)) {
      Console.WriteLine(testString + " is an anagram of " + input);
    } else {
      Console.WriteLine(testString + " is NOT an anagram of " + input);
    }
  }

  static List<string> GetPermutations(string input) {
    List<string> result = new List<string>();
    if (input.Length == 1) {
      result.Add(input);
    } else {
      for (int i = 0; i < input.Length; i++) {
        string partialString = input.Substring(0, i) + input.Substring(i + 1);
        List<string> partialPermutations = GetPermutations(partialString);
        for (int j = 0; j < partialPermutations.Count; j++) {
          result.Add(input[i] + partialPermutations[j]);
        }
      }
    }
    return result;
  }
}
1253 chars
41 lines