Reputation: 2711
I want to compare a collection of strings and return the the equal parts until a not equal part occurs. (and remove traling whitespace).
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 that 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 that this is something that can be done in a few lines and I am overdoing it. Do you guys have any suggestions?
Upvotes: 3
Views: 209
Reputation: 67345
Here's a version that uses less LINQ than some of the other answers and might possibly be more performant.
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();
}
Upvotes: 1
Reputation: 460278
Here's a different method which does what you want. I looks for the longest common substring from left to right using a 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;
}
Upvotes: 1
Reputation: 7140
This little function does 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();
}
Upvotes: 2
Reputation: 203821
You can Zip
two strings together, take the 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've solved the problem for the case of combining two strings, you can easily apply it to a sequence of strings:
public static string LargestCommonPrefix(IEnumerable<string> strings)
{
return strings.Aggregate(LargestCommonPrefix);
}
Upvotes: 6