Problem:
Score : 500 points

Problem Statement

You are given a string S of length N consisting of lowercase English letters.

Process Q queries of the following two types:

Type 1: change the i_q-th character of S to c_q. (Do nothing if the i_q-th character is already c_q.)

Type 2: answer the number of different characters occurring in the substring of S between the l_q-th and r_q-th characters (inclusive).

Constraints

N, Q, i_q, l_q, and r_q are integers.

S is a string consisting of lowercase English letters.

c_q is a lowercase English letter.

1 \leq N \leq 500000

1 \leq Q \leq 20000

|S| = N

1 \leq i_q \leq N

1 \leq l_q \leq r_q \leq N

There is at least one query of type 2 in each testcase.

Input

Input is given from Standard Input in the following format:

N
S
Q
Query_1
\vdots
Query_Q

Here, Query_i in the 4-th through (Q+3)-th lines is one of the following:

1 i_q c_q

2 l_q r_q

Output

For each query of type 2, print a line containing the answer.

Sample Input 1

7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7

Sample Output 1

3
1
5

In the first query, cdbb contains three kinds of letters: b , c , and d, so we print 3.

In the second query, S is modified to abcdzbd.

In the third query, a contains one kind of letter: a, so we print 1.

In the fourth query, S is modified to abcazbd.

In the fifth query, S does not change and is still abcazbd.

In the sixth query, abcazbd contains five kinds of letters: a, b, c, d, and z, so we print 5.

Solution in Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.*

fun main(args: Array<String>) {
    val N = readLine()!!.toInt()
    val S = readLine()!!
    val Q = readLine()!!.toInt()

    val s = S.toCharArray()

    val t = mutableMapOf<Char, TreeSet<Int>>()
    for(i in 0 until 26){
        t['a' + i] = sortedSetOf()
    }
    for(i in s.indices){
        t[s[i]]!!.add(i)
    }

    repeat(Q){
        val q = readLine()!!.split(" ")
        if(q[0] == "1"){
            val i = q[1].toInt() - 1
            val c = q[2][0]
            t[s[i]]!!.remove(i)
            s[i] = c
            t[c]!!.add(i)
        }else{
            val l = q[1].toInt() - 1
            val r = q[2].toInt() - 1
            (0 until 26)
                .filter { i ->
                    val p = t['a' + i]!!.higher(l - 1) ?: N
                    p <= r
                }
                .count()
                .let { println(it) }
        }
    }
}