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)

#include<cstdio>
#include<iostream>
#define int long long
using namespace std;
int data[26][500005];
int n;
inline int lowbit(int x){return x&(-x);}
void change(int z,int x,int y)
{
    for(int i=x;i<=n;i+=lowbit(i))
    {
        data[z][i]+=y;
    }
}
int query(int z,int x)
{
    if(x==0)return 0;
    int ans=0;
    for(int i=x;i;i-=lowbit(i))
    {
        ans+=data[z][i];
    }
    return ans;
}
char s[500005];int xx;int l,r;
signed main()
{
	cin>>n;
	cin>>s+1;
	for(int i=1;i<=n;i++)
	{
		change(s[i]-'a',i,1);
	}
    int m;cin>>m;
    for(int i=1;i<=m;i++)
    {
    	cin>>xx;
    	if(xx==1)
    	{
			int weizhi;
			char c;
			cin>>weizhi;
			cin>>c;
			if(s[weizhi]!=c)
			{
				change(s[weizhi]-'a',weizhi,-1);
				change(c-'a',weizhi,1);
				s[weizhi]=c;
			}
		}
		else if(xx==2)
		{
			cin>>l>>r;
			int ans=0;
			for(int j=0;j<26;j++)
			{
				if((query(j,r)-query(j,l-1))>=1)
				{
					ans++;
				}
			}
			cout<<ans<<endl;
		}
	}
}