longest common substring

// C++ program using to find length of the  
// longest common substring  recursion 
#include <iostream> 
  
using namespace std; 
  
string X,Y; 
  
// Returns length of function for longest common   
// substring of X[0..m-1] and Y[0..n-1]  
int lcs(int i, int j, int count)  
{ 
      
    if (i == 0 || j == 0) 
        return count; 
          
    if (X[i-1] == Y[j-1]) { 
        count = lcs(i - 1, j - 1, count + 1); 
    } 
        count = max(count, max(lcs( i, j - 1, 0), lcs( i - 1, j, 0))); 
    return count; 
} 
  
// Driver code 
int main() 
{ 
int n,m; 
  
X = "abcdxyz";  
Y = "xyzabcd"; 
  
n=X.size(); 
m=Y.size(); 
  
cout<<lcs(n,m,0); 
  
    return 0; 
} 

/* Dynamic Programming solution to find length of the  
   longest common substring */
#include<iostream> 
#include<string.h> 
using namespace std; 
  
/* Returns length of longest common substring of X[0..m-1]  
   and Y[0..n-1] */
int LCSubStr(char *X, char *Y, int m, int n) 
{ 
    // Create a table to store lengths of longest 
    // common suffixes of substrings.   Note that 
    // LCSuff[i][j] contains length of longest 
    // common suffix of X[0..i-1] and Y[0..j-1].  
  
    int LCSuff[m+1][n+1]; 
    int result = 0;  // To store length of the  
                     // longest common substring 
  
    /* Following steps build LCSuff[m+1][n+1] in 
        bottom up fashion. */
    for (int i=0; i<=m; i++) 
    { 
        for (int j=0; j<=n; j++) 
        { 
  
            // The first row and first column  
            // entries have no logical meaning,  
            // they are used only for simplicity  
            // of program 
            if (i == 0 || j == 0) 
                LCSuff[i][j] = 0; 
  
            else if (X[i-1] == Y[j-1]) 
            { 
                LCSuff[i][j] = LCSuff[i-1][j-1] + 1; 
                result = max(result, LCSuff[i][j]); 
            } 
            else LCSuff[i][j] = 0; 
        } 
    } 
    return result; 
} 
  
/* Driver program to test above function */
int main() 
{ 
    char X[] = "OldSite:GeeksforGeeks.org"; 
    char Y[] = "NewSite:GeeksQuiz.com"; 
  
    int m = strlen(X); 
    int n = strlen(Y); 
  
    cout << "Length of Longest Common Substring is " 
         << LCSubStr(X, Y, m, n); 
    return 0; 
}