Function to return the frequency of the given character in the sub - string str [ l ... r ]
def getFrequency ( ch , l , r ) : NEW_LINE INDENT if l == 0 : NEW_LINE INDENT return freq [ ord ( ch ) ] [ r ] NEW_LINE DEDENT else : NEW_LINE INDENT return ( freq [ ord ( ch ) ] [ r ] - freq [ ord ( ch ) ] [ l - 1 ] ) NEW_LINE DEDENT DEDENT