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 (1.15.1) (judge verdict: Accepted)

use std::io::*;

mod segment_tree {
    pub struct SegmentTree<T, F> {
        size: usize,
        data: Vec<T>,
        identity: T,
        operation: F,
    }

    impl<T: Copy + Clone, F: Fn(T, T) -> T> SegmentTree<T, F> {
        pub fn new(n: usize, id: T, op: F) -> SegmentTree<T, F> {
            let mut size = 1;
            while size < n {
                size <<= 1;
            }
            SegmentTree {
                size: size,
                data: vec![id; size * 2],
                identity: id,
                operation: op,
            }
        }

        pub fn update(&mut self, mut i: usize, x: T) {
            i += self.size;
            self.data[i] = x;
            i >>= 1;
            while i > 0 {
                self.data[i] = (self.operation)(self.data[i * 2], self.data[i * 2 + 1]);
                i >>= 1;
            }
        }
        pub fn query(&self, mut l: usize, mut r: usize) -> T {
            let mut a = self.identity;
            let mut b = self.identity;
            l += self.size;
            r += self.size;
            while l < r {
                if (l & 1) == 1 {
                    a = (self.operation)(a, self.data[l]);
                    l += 1;
                }
                if (r & 1) == 1 {
                    r -= 1;
                    b = (self.operation)(self.data[r], b);
                }
                l >>= 1;
                r >>= 1;
            }
            (self.operation)(a, b)
        }
    }
}

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let s: Vec<usize> = itr
        .next()
        .unwrap()
        .chars()
        .map(|c| c as usize - 'a' as usize)
        .collect();
    let q: usize = itr.next().unwrap().parse().unwrap();

    // 区間和をとると長さ26のビット列が返る
    let mut count = segment_tree::SegmentTree::new(n, 0u32, |x, y| x | y);
    for i in 0..s.len() {
        count.update(i, 1 << s[i]);
    }

    let mut out = Vec::new();
    for _ in 0..q {
        let c: usize = itr.next().unwrap().parse().unwrap();
        if c == 1 {
            let i: usize = itr.next().unwrap().parse::<usize>().unwrap() - 1;
            let tmp: Vec<char> = itr.next().unwrap().chars().collect();
            let c: usize = tmp[0] as usize - 'a' as usize;
            count.update(i, 1 << c);
        } else {
            let l: usize = itr.next().unwrap().parse().unwrap();
            let r: usize = itr.next().unwrap().parse().unwrap();
            writeln!(out, "{}", count.query(l - 1, r).count_ones()).ok();
        }
    }
    stdout().write_all(&out).unwrap();
}