longest common substring

siva nagarjuna

10y861Learn iOS Programming

hi,

please write a code for longest common sub string in two strings in c#?

Input:s1="siva nagarjuna"

s2="hello nagarjuna how r u"

output:nagarjuna

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Midhun Tp10y ago
Hi,
Here is the code for that -
public string LongestCommonSubstring(string str1, string str2)
{
string sequence = string.Empty;
if (String.IsNullOrEmpty(str1) || String.IsNullOrEmpty(str2))
return "";
int[,] num = new int[str1.Length, str2.Length];
int maxlen = 0;
int lastSubsBegin = 0;
StringBuilder sequenceBuilder = new StringBuilder();
for (int i = 0; i < str1.Length; i++)
{
for (int j = 0; j < str2.Length; j++)
{
if (str1[i] != str2[j])
num[i, j] = 0;
else
{
if ((i == 0) || (j == 0))
num[i, j] = 1;
else
num[i, j] = 1 + num[i - 1, j - 1];
if (num[i, j] > maxlen)
{
maxlen = num[i, j];
int thisSubsBegin = i - num[i, j] + 1;
if (lastSubsBegin == thisSubsBegin)
{//if the current LCS is the same as the last time this block ran
sequenceBuilder.Append(str1[i]);
}
else //this block resets the string builder if a different LCS is found
{
lastSubsBegin = thisSubsBegin;
sequenceBuilder.Length = 0; //clear it
sequenceBuilder.Append(str1.Substring(lastSubsBegin, (i + 1) - lastSubsBegin));
}
}
}
}
}
sequence = sequenceBuilder.ToString();
return sequence;
}
Pass your strings to above function. Yo will get the result.
Reference : https://en.wikibooks.org/wiki/Algorithm_Implementation/Strings/Longest_common_substring
Manas Mohapatra10y ago
Try with below code:
string s1 = "siva nagarjuna";
            string s2 = "hello nagarjuna how r  siva u";
            string tempStr;

            List<string> stringList = new List<string>();

            if (s1.Length > s2.Length)
            {
                tempStr = s1;
                s1 = s2;
                s2 = tempStr;
            }

            foreach (string temp in s1.Split(' '))
            {
                if (s2.Contains(temp))
                {
                    stringList.Add(temp);
                }
            }

            string bigList2 = (from s in stringList
                              where s.Length == stringList.Max(a => a.Length)
                              select s).FirstOrDefault();
siva nagarjuna10y ago
thanks for u r help
Iwant know the code for in thi case also
Input:s1="sivanagarjuna";
s2="hellonagarjunahowru"
output:nagarjuna
Midhun Tp10y ago
Hi,
Try below code -
string s1 = "siva nagarjuna";
string s2 = "hello nagarjuna how r u";
string[] tempArr1 = s1.Split(' ');
string[] tempArr2 = s2.Split(' ');
int len = 0;
string response = "";
for (int i = 0; i < tempArr2.Length; i++)
{
if (tempArr1.Contains(tempArr2[i]))
{
if (tempArr2[i].Length > len)
{
response = tempArr2[i];
len = tempArr2[i].Length;
}
}
}
Response.Write(response);
This will give the longest common words in two strings