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 C++14 (GCC 5.4.1) (judge verdict: Accepted)


// E - Simple String Queries

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
// const int INF = 2147483647;
// const ll INF = 9223372036854775807;
// const ll MOD = 1e9 + 7;

int main() {
	int N, Q;
	string S;
	cin >> N >> S >> Q;

	map<char, set<int>> sets;

	for (int i=0; i<S.size(); i++) {
		sets[S[i]].insert(i);
	}

	char c;
	int t, i, l, r;
	vector<int> ans;
	for (int k=0; k<Q; k++) {
		cin >> t;
		if (t == 1) {
			cin >> i >> c;
			i--;
			for (char ch='a'; ch<='z'; ch++) {
				sets[ch].erase(i);
			}
			sets[c].insert(i);
		}

		if (t == 2) {
			cin >> l >> r;
			l--;
			r--;
			int cnt = 0;
			for (char ch='a'; ch<='z'; ch++) {
				auto itr = sets[ch].lower_bound(l);
				if (itr != sets[ch].end() && *itr <= r) cnt++;
			}
			ans.push_back(cnt);
		}
	}

	for (int a : ans) {
		cout << a << endl;
	}

	return 0;
}