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 Rust (1.42.0) (judge verdict: Accepted)

#![allow(non_snake_case, unused_mut)]
//use petgraph::unionfind::UnionFind;
use proconio::marker::Usize1;
use proconio::{fastout, input, marker::*};
use std::collections::*;

#[fastout()]
fn main() {
    input! {
        N:usize, mut S:Chars, Q:usize,
    }
    let mut set = vec![BTreeSet::new(); 26];
    let ctoi = |c| (c as u8 - b'a') as usize;
    for i in 0..N {
        set[ctoi(S[i])].insert(i);
    }

    for _ in 0..Q {
        input! {query:i32}
        if query == 1 {
            input! {iq:Usize1,cq:char}
            let sq = S[iq];
            if sq == cq {
                continue;
            };
            set[ctoi(sq)].remove(&iq);
            set[ctoi(cq)].insert(iq);
            S[iq] = cq;
        } else {
            // queary 2の場合
            input! {lq:Usize1, rq:Usize1}
            let mut ans = 0;
            for c in b'a'..=b'z' {
                let i = (c - b'a') as usize;
                let mut p = set[i].range(lq..=rq).peekable();
                if p.peek().is_some() {
                    ans += 1;
                }
            }

            println!("{}", ans);
        }
    }
}