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 ( int i = 0 ; i <= m ; i ++ ) { for ( int 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 ; result = max ( result , len [ currRow ] [ j ] ) ; } else { len [ currRow ] [ j ] = 0 ; } }