Find a common string within a list of strings

Question

I\'m very close on this. I got a question posed to me yesterday by a developer if I could have a look at this.

I feel close, but I think some people here would apprec

Answer 1

This works better than my first approach(striked out).

You can use following extension to get all substrings of the shortest string in the list(for efficiency):

public static IEnumerable getAllSubstrings(this string word)
{
    return from charIndex1 in Enumerable.Range(0, word.Length)
           from charIndex2 in Enumerable.Range(0, word.Length - charIndex1 + 1)
           where charIndex2 > 0
           select word.Substring(charIndex1, charIndex2);
}

• now order these substrings by Length(longest first)
• look if all other strings(excluding the string itself because that test is redundant) contain that substring (Enumerable.All returns immediately if one string doesn't contain a given substring)
• if one string appears in all others you have found the longest common substring
• otherwise repeat that until you've checked all substrings(if no common string was found)

---

string shortest = list.OrderBy(s => s.Length).First();
IEnumerable shortestSubstrings = shortest
    .getAllSubstrings()
    .OrderByDescending(s => s.Length);
var other = list.Where(s => s != shortest).ToArray();
string longestCommonIntersection = string.Empty;
foreach (string subStr in shortestSubstrings)
{
    bool allContains = other.All(s => s.Contains(subStr));
    if (allContains)
    {
        longestCommonIntersection = subStr;
        break;
    }
}

DEMO