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)

fn main() {
	let mut s = String::new();
	use std::io::{Read, Write};
	std::io::stdin().read_to_string(&mut s).unwrap();
	let mut s = s.split_whitespace();
	let _n: usize = s.next().unwrap().parse().unwrap();
	let a: Vec<u32> = s.next().unwrap().bytes().map(|c| 1 << (c - b'a')).collect();
	let mut st = SegmentTree::construct(a, 0, |a, b| a | b);
	let q: usize = s.next().unwrap().parse().unwrap();
	let out = std::io::stdout();
	let mut out = std::io::BufWriter::new(out.lock());
	for _ in 0..q {
		if s.next().unwrap() == "1" {
			let i: usize = s.next().unwrap().parse().unwrap();
			let c: u32 = 1 << (s.next().unwrap().bytes().next().unwrap() - b'a');
			st.set(i - 1, c);
		} else {
			let l: usize = s.next().unwrap().parse().unwrap();
			let r: usize = s.next().unwrap().parse().unwrap();
			writeln!(out, "{}", st.query(l - 1, r).count_ones()).unwrap();
		}
	}
}

pub struct SegmentTree<T, F> {
	n: usize,
	data: Vec<T>,
	e: T,
	op: F,
}

impl<T, F> SegmentTree<T, F>
where
	T: Clone,
	F: Fn(T, T) -> T,
{
	pub fn new(n: usize, e: T, op: F) -> SegmentTree<T, F> {
		SegmentTree { n: n, data: vec![e.clone(); n << 1], e: e, op: op }
	}

	pub fn construct(a: Vec<T>, e: T, op: F) -> SegmentTree<T, F> {
		let n = a.len();
		let mut data = vec![e.clone(); n];
		data.extend(a);
		for i in (1..n).rev() {
			data[i] = op(data[i << 1].clone(), data[i << 1 | 1].clone());
		}
		SegmentTree { n: n, data: data, e: e, op: op }
	}

	pub fn query(&self, s: usize, t: usize) -> T {
		let mut l = self.e.clone();
		let mut r = self.e.clone();
		let mut s = s + self.n;
		let mut t = t + self.n;
		while s < t {
			if s & 1 != 0 {
				l = (self.op)(l, self.data[s].clone());
				s += 1;
			}
			if t & 1 != 0 {
				r = (self.op)(self.data[t - 1].clone(), r);
			}
			s >>= 1;
			t >>= 1;
		}
		(self.op)(l, r)
	}

	pub fn set(&mut self, i: usize, v: T) {
		let mut i = i + self.n;
		self.data[i] = v;
		while {
			i >>= 1;
			i > 0
		} {
			self.data[i] = (self.op)(self.data[i << 1].clone(), self.data[i << 1 | 1].clone());
		}
	}
}