Returns length of LCS for X [ 0. . m - 1 ] , Y [ 0. . n - 1 ]
static int lcs ( String X , String Y , int m , int n ) { if ( m == 0 n == 0 ) { return 0 ; } if ( X . charAt ( m - 1 ) == Y . charAt ( n - 1 ) ) { return 1 + lcs ( X , Y , m - 1 , n - 1 ) ; } else { return Math . max ( lcs ( X , Y , m , n - 1 ) , lcs ( X , Y , m - 1 , n ) ) ; } }