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.*

var n = -1
val bit = Array(26) {Array(500002) {0}}

// 1-indexed
fun sum(alpha:Int, i: Int): Int{
    var res = 0
    var j = i
    while (j > 0) {
        res += bit[alpha][j];
        j -= j and (-j)
    }
    return res
}

fun sum(alpha: Int, i: Int, j: Int): Int {
    return sum(alpha, j) - sum(alpha, i - 1)
}

fun add(alpha: Int, i: Int, value: Int){
    var j = i
    while(j <= n){
        bit[alpha][j] += value
        j += j and (-j)
    }
}

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    n = sc.nextInt()
    val s = sc.next().toCharArray()
    s.forEachIndexed { index, c -> add(c - 'a', index + 1, 1) }
    val q = sc.nextInt()
    repeat(q) {
        val op = sc.nextInt()
        if (op == 1) {
            val i = sc.nextInt()
            val from = s[i - 1] - 'a'
            val to = sc.next()[0] - 'a'
            s[i - 1] = 'a' + to
            add(from, i, -1)
            add(to, i, 1)
        } else {
            val l = sc.nextInt()
            val r = sc.nextInt()
            println((0 until 26).map { if(sum(it, l, r) > 0) 1 else 0 }.sum())
        }
    }
}