Print the longest common substring

<script>
// Javascript implementation to print the longest common substring
    
    /* function to find and print the longest common
       substring of X[0..m-1] and Y[0..n-1] */
    function printLCSubStr(X,Y,m,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]. The first row and first column entries
        // have no logical meaning, they are used only for
        // simplicity of program
        let LCSuff = new Array(m+1);
        
        // To store length of the longest common substring
        let len = 0;
 
        // To store the index of the cell which contains the
        // maximum value. This cell's index helps in building
        // up the longest common substring from right to left.
        let row = 0, col = 0;
 
        /* Following steps build LCSuff[m+1][n+1] in bottom
           up fashion. */
        for (let i = 0; i <= m; i++) {
            LCSuff[i] = Array(n+1);
            for (let j = 0; j <= n; j++) {
                LCSuff[i][j]=0;    
                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;
                    if (len < LCSuff[i][j]) {
                        len = LCSuff[i][j];
                        row = i;
                        col = j;
                    }
                }
                else
                    LCSuff[i][j] = 0;
            }
        }
 
        // if true, then no common substring exists
        if (len == 0) {
            document.write("No Common Substring");
            return;
        }
 
        // allocate space for the longest common substring
        let resultStr = "";
 
        // traverse up diagonally form the (row, col) cell
        // until LCSuff[row][col] != 0
        while (LCSuff[row][col] != 0) {
            resultStr = X[row-1] + resultStr; // or Y[col-1]
            --len;
 
            // move diagonally up to previous cell
            row--;
            col--;
        }
 
        // required longest common substring
        document.write(resultStr);
    }
    
    /* Driver program to test above function */
    let X = "OldSite:GeeksforGeeks.org";
    let Y = "NewSite:GeeksQuiz.com";
    let m = X.length;
    let n = Y.length;
    printLCSubStr(X, Y, m, n);
    
    //This code is contributed by rag2127
    
</script>

<script>
// Space optimized javascript implementation to print
// longest common substring.    
    
    // Function to find longest common substring.
    function LCSubStr(X,Y)
    {
        // Find length of both the strings.
    let m = X.length;
    let n = Y.length;
 
    // Variable to store length of longest
    // common substring.
    let result = 0;
 
    // Variable to store ending point of
    // longest common substring in X.
    let end;
 
    // Matrix to store result of two
    // consecutive rows at a time.
    let len= new Array(2);
    for(let i=0;i<len.length;i++)
    {
        len[i]=new Array(n);
        for(let j=0;j<n;j++)
        {
            len[i][j]=0;
        }
    }
 
    // Variable to represent which row of
    // matrix is current row.
    let currRow = 0;
 
    // For a particular value of i and j,
    // len[currRow][j] stores length of longest
    // common substring in string X[0..i] and Y[0..j].
    for (let i = 0; i <= m; i++) {
        for (let j = 0; j <= n; j++) {
            if (i == 0 || j == 0) {
                len[currRow][j] = 0;
            }
            else if (X[i - 1] == Y[j - 1]) {
                len[currRow][j] = len[1 - currRow][j - 1] + 1;
                if (len[currRow][j] > result) {
                    result = len[currRow][j];
                    end = i - 1;
                }
            }
            else {
                len[currRow][j] = 0;
            }
        }
 
        // Make current row as previous row and
        // previous row as new current row.
        currRow = 1 - currRow;
    }
 
    // If there is no common substring, print -1.
    if (result == 0) {
        return "-1";
    }
 
    // Longest common substring is from index
    // end - result + 1 to index end in X.
    return X.substr(end - result + 1, result);
    }
    
    // Driver Code
    let X = "GeeksforGeeks";
    let Y = "GeeksQuiz";
    // function call
    document.write(LCSubStr(X, Y));
    
    
    // This code is contributed by avanitrachhadiya2155
</script>