For each character in input strings , increment count in the corresponding count array
for ( i = 0 ; i < str1 . length ; i ++ ) { count [ str1 [ i ] . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ] ++ ; count [ str2 [ i ] . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ] -- ; }