Really Simple Anagram Solver

• Download source code - 2.45 KB

Introduction

I will be back! This is my first post since 5 years ago! If you have been interviewed by Microsoft before, you might have come across this kind of recursive questions. I have written a few different solutions, and this is so far my latest, and maybe the smallest one.

Background

Always good to get your mind juggled a little bit. If you are in the middle of a Tech Access for a job, hope it can help and good luck!

Using the Code

If you have VS2010, you will know how to run this project. Here is the recursive method:

static void GenerateAnagram(IList<string> result, string prefix, string src)
{
    if (src.Length == 0)
    {
        result.Add(prefix);
        return;
    }

    for (int i = 0; i < src.Length; i++ )
    {
        string tempPrefix = src[i].ToString();
        string newSrc = src.Substring(0, i) + src.Substring(i + 1);
        var temp = new List<string>();
        GenerateAnagram(temp, tempPrefix, newSrc);
        foreach (var s in temp)
        {
            result.Add(prefix + s);
        }
    }
}

And here is how to call it:

var result = new List<string>();
GenerateAnagram(result, "", "ABC");

And after one of my reader pointed out the memory problem, here is another approach using recursion:

static IEnumerable<string> GenerateAnagramAlt(string src)
{
    if (src.Length == 0) yield break;
    if (src.Length == 1) yield return src;

    foreach (string rest in GenerateAnagramAlt(src.Substring(1)))
    {
        for (int i = 0; i < src.Length; i++)
        {
            string temp = rest.Substring(0, i) + src[0] + rest.Substring(i);
            yield return temp;
        }
    }
}

I prefer this one as it doesn't have the memory limitation and nearly twice faster when n >= 9 characters. I like its IEnumberable syntax as well! I have updated a new project to include the source file. Thanks goes to my friend ajasin1, who came up with this.

Points of Interest

I have not included logic to filter duplicated cases, as it can be done using LINQ quite easily.

History

• 08-09-2011: First posted.
• 09-09-2011: 2.0 posted for GenerateAnagramAlt.