Count the number of different characters in both strings
for ( let i = 0 ; i < n ; i ++ ) { count1 [ s1 [ i ] . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ] += 1 ; count2 [ s2 [ i ] . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ] += 1 ; }