mark presence of each character as 0 in the hash table 'present[]
' NEW_LINE INDENT present = [ 0 ] * MAX_CHAR NEW_LINE for i in range ( 0 , MAX_CHAR ) : NEW_LINE INDENT present [ i ] = 0 NEW_LINE DEDENT l1 = len ( str1 ) NEW_LINE l2 = len ( str2 ) NEW_LINE DEDENT