Compare strings for equality
I want to compare a set of strings and return equal parts until there is not an equal part. (and remove the simplest spaces).
Example:
List<string> strList = new List<string>
{
"string xyz stop",
"string abc stop",
"string qrt stop"
};
string result = GetEqualName(strList); // This should return "string"
I made the following method which works
string GetEqualName(IEnumerable<string> strList)
{
string outString = "";
bool firstTime = true;
foreach (var subString in strList)
{
if (firstTime)
{
outString = subString;
firstTime = false;
}
else
{
string stringBuilder = "";
for (int i = 0; i < outString.Count(); i++)
{
if (outString[i] == subString[i])
stringBuilder = stringBuilder + outString[i];
else
break;
}
outString = stringBuilder;
}
}
outString = outString.TrimEnd(' '); // Remove traling whitespace
return outString;
}
I just feel like this is something that can be done in a few lines and I'm overdoing it. Do you have any suggestions?
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You can Zip
two strings together, take pairs that are equal, and then create a string of those characters.
public static string LargestCommonPrefix(string first, string second)
{
return new string(first.Zip(second, Tuple.Create)
.TakeWhile(pair => pair.Item1 == pair.Item2)
.Select(pair => pair.Item1)
.ToArray());
}
Once you solve the problem for concatenating two strings, you can easily apply it to a sequence of strings:
public static string LargestCommonPrefix(IEnumerable<string> strings)
{
return strings.Aggregate(LargestCommonPrefix);
}
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This little feature is basically the same as your version, but shorter.
string GetEqualName(IEnumerable<string> strList)
{
int limit = strList.Min(s => s.Length);
int i = 0;
for (; i < limit; i++)
{
if (strList.Select(s => s.Substring(0,i+1)).Distinct().Count() > 1)
{
break;
}
}
return strList.First().Substring(0, i).Trim();
}
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Here's another method that does what you want. I am looking for the longest common substring from left to right using HashSet<string>
:
string GetCommonStartsWith(IEnumerable<string> strList, StringComparer comparer = null)
{
if(!strList.Any() || strList.Any(str => string.IsNullOrEmpty(str)))
return null;
if(!strList.Skip(1).Any())
return strList.First(); // only one
if(comparer == null) comparer = StringComparer.CurrentCulture;
int commonLength = strList.Min(str => str.Length);
for (int length = commonLength; length > 0; length--)
{
HashSet<string> duptester = new HashSet<string>(comparer);
string first = strList.First().Substring(0, length).TrimEnd();
duptester.Add(first);
bool allEqual = strList.Skip(1)
.All(str => !duptester.Add(str.Substring(0, length).TrimEnd()));
if (allEqual)
return first;
}
return null;
}
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Here's a version that uses less LINQ than some of the other answers, and might be more efficient.
string GetEqualName(IEnumerable<string> strList)
{
StringBuilder builder = new StringBuilder();
int minLength = strList.Min(s => s.Length);
for (int i = 0; i < minLength; i++)
{
char? c = null;
foreach (var s in strList)
{
if (c == null)
c = s[i];
else if (s[i] != c)
return builder.ToString().TrimEnd();
}
builder.Append(c);
}
return builder.ToString().TrimEnd();
}
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