Find lengths of two strings
let m = X . length , n = Y . length ; let L = new Array ( 2 ) ; for ( let i = 0 ; i < 2 ; i ++ ) { L [ i ] = new Array ( n + 1 ) ; for ( let j = 0 ; j < n + 1 ; j ++ ) { L [ i ] [ j ] = 0 ; } }