return the number of common subsequence in two strings
function CommomSubsequencesCount ( s , t ) { var n1 = s . length ; var n2 = t . length ; var dp = Array . from ( Array ( n1 + 1 ) , ( ) => Array ( n2 + 1 ) ) ; for ( var i = 0 ; i <= n1 ; i ++ ) { for ( var j = 0 ; j <= n2 ; j ++ ) { dp [ i ] [ j ] = 0 ; } }