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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using static System.Console;
using static System.Math;
 
public class Solve{
    static public int mod = 1000000007;
    static public string al = "abcdefghijklmnopqrstuvwxyz";
    public static void Main(){
        // 方針
        //
        var n = rint();
        var rms = new bitRMS(n);
        var s = rstr();
        for(int i=0;i<n;i++){
            var c = 1 << al.IndexOf(s[i].ToString());
            rms.Change(i,c);
            //WriteLine(c);
        }
        var que = rint();
        for(int i=0;i<que;i++){
            var str = stra();
            var le = int.Parse(str[1])-1;
            if(str[0] == "1"){
                var c = 1 << al.IndexOf(str[2]);
                rms.Change(le,c);
            }else{
                var ri = int.Parse(str[2])-1;
                var ans = rms.Query(le,ri);
                var count = 0;
                while(ans > 0){
                    if(ans %2 ==1) count++;
                    ans = ans>>1;
                }
                WriteLine(count);
            }
        }
	
	
    }
    public static void swap(ref int a,ref int b){int temp = a;a= b;b = temp;}
    static void charswap(ref char a,ref char b){char temp = a;a= b;b = temp;}
    static int ncr(int n,int r){if(n<r)return 0;r = Min(r,n-r);long nn = 1;for(int i=n-r+1;i<=n;i++){nn = nn*i%mod;}long rr = 1;for(int i=1;i<=r;i++){rr = rr*i%mod;}rr = square((int)rr,mod-2);nn = nn * rr %mod;return (int)nn;}
    // a^b mod
    static int square(int a,int b){string binary = Convert.ToString(b,2);int bileng = binary.Length;long a_power = a;long value = 1;for(int i=bileng-1;i>=0;i--){if(binary[i] == '1'){value = value*a_power%mod;}a_power = a_power*a_power%mod;}return (int)value;}
    static int square2(int a,int b){long output = 1;var list = new List<long>();int sh = 1;long n = a;list.Add(a);while(sh < b){sh *= 2;n = n*n%mod;list.Add(n);}for(int i=list.Count-1;i>=0;i--){if(b > sh){b -= sh;sh /= 2;output = output*list[i]%mod;}}return (int)output;}
    //各種読取
    static string rstr(){ return ReadLine(); }
    static int rint(){ return int.Parse(ReadLine()); }
    static long rlong(){ return long.Parse(ReadLine()); }
    static string[] stra(){ return ReadLine().Split(' '); }
    static char[] chara(){ string[] a=stra();string b="";for(int i=0;i<a.Length;i++){b+=a[i];}return b.ToCharArray();}
    static int[] inta(){ string[] read_str_array = ReadLine().Split(' '); int[] return_int_array = new int[read_str_array.Length]; for(int countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_int_array[countup_i] = int.Parse(read_str_array[countup_i]); } return return_int_array; }
    static int[,] inta2(int num_array,int in_array){ int[,] int_array2 = new int[num_array,in_array]; for(int i=0;i<num_array;i++){ int[] temp_array = inta(); for(int j=0;j<in_array;j++){ int_array2[i,j] = temp_array[j]; } } return int_array2; }
    static long[] longa(){ string[] read_str_array = ReadLine().Split(' '); long[] return_long_array = new long[read_str_array.Length]; for(long countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_long_array[countup_i] = long.Parse(read_str_array[countup_i]); } return return_long_array; }
    static double[] doublea(){ string[] read_str_array = ReadLine().Split(' '); double[] return_double_array = new double[read_str_array.Length]; for(long countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_double_array[countup_i] = long.Parse(read_str_array[countup_i]); } return return_double_array; }
    // -----------------------------
    static long divideup(long divided,long divid){ long temp_divide = divided/divid; if(divided % divid > 0){ temp_divide++; } return temp_divide; }
    static long GCD(long a,long b){ if(a < b){ long temp = a; a = b; b = temp; } if(a % b == 0){ return b; } else{ long temp = b; b = a%b; a = temp; return GCD(a,b); } }
    static long LCM(long a,long b){ return a * b / GCD(a,b); }
    static void WriteArray(int[,] a,int b,int c){for(int i=0;i<b;i++){for(int j=0;j<c;j++){if(j!=0) Write(" ");Write(a[i,j]);}WriteLine();}}
}

class UnionFind{
    private int[] _unionfind;
    private int[] _unionfind_size;
    
    public UnionFind(int a){
        _unionfind = new int[a];
        _unionfind_size = new int[a];
        for(int i=0;i<a;i++){
            _unionfind[i] = i;
            _unionfind_size[i] = 1;
        }
    }
    
    public int root(int x){
        if(_unionfind[x] == x) return x;
        return _unionfind[x] = root(_unionfind[x]);
    }
    
    public void unite(int a,int b){
        a = root(a);
        b = root(b);
        if(a == b) return;
        if(_unionfind_size[a] < _unionfind_size[b]){
            int temp = a;
            a = b;
            b = temp;
        }
        _unionfind[b] = a;
        _unionfind_size[a] += _unionfind_size[b];
    }
    
    public bool same(int a,int b){
        return root(a) == root(b);
    }
    
    public int size(int x){
        return _unionfind_size[root(x)];
    }
}

class PriorityQueue{
    private List<int> _priorityqueue = new List<int>();
    
    public void Enqueue(int a){
        _priorityqueue.Add(a);
        int num = _priorityqueue.Count-1;
        while(true){
            if(num == 0) break;
            if(_priorityqueue[(num-1)/2] < _priorityqueue[num]){ //大小逆の時弄るとこ
                int temp = _priorityqueue[(num-1)/2];
                _priorityqueue[(num-1)/2] = _priorityqueue[num];
                _priorityqueue[num] = temp;
                num = (num-1)/2;
            }else{
                break;
            }
        }
    }
    
    public int Dequeue(){
        int re = _priorityqueue[0];
        int temp = _priorityqueue[0];
        _priorityqueue[0] = _priorityqueue[_priorityqueue.Count-1];
        _priorityqueue[_priorityqueue.Count-1] = temp;
        _priorityqueue.RemoveAt(_priorityqueue.Count-1);
        int num = 0;
        while(true){
            int swapnum = -1;
            if((num+1)*2 < _priorityqueue.Count){
                if(_priorityqueue[num*2+1] > _priorityqueue[(num+1)*2]){ //大小逆の時弄るとこ
                    swapnum = num*2+1;
                }else{
                    swapnum = (num+1)*2;
                }
            }else if(num*2+1 < _priorityqueue.Count){
                swapnum = num*2+1;
            }
            if(swapnum == -1) break;
            if(_priorityqueue[swapnum] > _priorityqueue[num]){ //大小逆の時弄るとこ
                temp = _priorityqueue[swapnum];
                _priorityqueue[swapnum] = _priorityqueue[num];
                _priorityqueue[num] = temp;
                num = swapnum;
            }else{
                break;
            }
        }
        return re;
    }
    
    public int Peek(){
        return _priorityqueue[0];
    }
    
    public int Count(){
        return _priorityqueue.Count;
    }
}
class PriorityQueue2{
    private List<int> _priorityqueue = new List<int>();
    private List<int> _accompany_info = new List<int>();
    
    public void Enqueue(int a,int b){
        _priorityqueue.Add(a);
        _accompany_info.Add(b);
        int num = _priorityqueue.Count-1;
        while(true){
            if(num == 0) break;
            if(_priorityqueue[(num-1)/2] > _priorityqueue[num]){ //大小逆の時弄るとこ
                int temp = _priorityqueue[(num-1)/2];
                  _priorityqueue[(num-1)/2] = _priorityqueue[num];
                  _priorityqueue[num] = temp;
                temp = _accompany_info[(num-1)/2];
                  _accompany_info[(num-1)/2] = _accompany_info[num];
                  _accompany_info[num] = temp;
                num = (num-1)/2;
            }else{
                break;
            }
        }
    }
    
    public int[] Dequeue(){
        var re = new int[]{_priorityqueue[0],_accompany_info[0]};
        var qcount = _priorityqueue.Count;
        var temp = _priorityqueue[0]; _priorityqueue[0] = _priorityqueue[qcount-1]; _priorityqueue[qcount-1] = temp;
        temp = _accompany_info[0]; _accompany_info[0] = _accompany_info[qcount-1]; _accompany_info[qcount-1] = temp;
        _priorityqueue.RemoveAt(qcount-1);
        _accompany_info.RemoveAt(qcount-1);
        int num = 0;
        while(true){
            int swapnum = -1;
            if((num+1)*2 < _priorityqueue.Count){
                if(_priorityqueue[num*2+1] < _priorityqueue[(num+1)*2]){ //大小逆の時弄るとこ
                    swapnum = num*2+1;
                }else{
                    swapnum = (num+1)*2;
                }
            }else if(num*2+1 < _priorityqueue.Count){
                swapnum = num*2+1;
            }
            if(swapnum == -1) break;
            if(_priorityqueue[swapnum] < _priorityqueue[num]){ //大小逆の時弄るとこ
                temp = _priorityqueue[swapnum];_priorityqueue[swapnum] = _priorityqueue[num];_priorityqueue[num] = temp;
                temp = _accompany_info[swapnum];_accompany_info[swapnum] = _accompany_info[num];_accompany_info[num] = temp;
                num = swapnum;
            }else{
                break;
            }
        }
        return re;
    }
    
    public int[] Peek(){
        var temp = new int[]{_priorityqueue[0],_accompany_info[0]};
        return temp;
    }
    
    public int Count(){
        return _priorityqueue.Count;
    }
}
class PriorityQueue3{
    private List<int> _priorityqueue = new List<int>();
    private List<int> _accompany_info = new List<int>();
    private List<int> _accompany_info2 = new List<int>();
    
    public void Enqueue(int a,int b,int c){
        _priorityqueue.Add(a);
        _accompany_info.Add(b);
        _accompany_info2.Add(c);
        int num = _priorityqueue.Count-1;
        while(true){
            if(num == 0) break;
            if(_priorityqueue[(num-1)/2] > _priorityqueue[num]){ //大小逆の時弄るとこ
                int temp = _priorityqueue[(num-1)/2];
                  _priorityqueue[(num-1)/2] = _priorityqueue[num];
                  _priorityqueue[num] = temp;
                temp = _accompany_info[(num-1)/2];
                  _accompany_info[(num-1)/2] = _accompany_info[num];
                  _accompany_info[num] = temp;
                  temp = _accompany_info2[(num-1)/2];
                  _accompany_info2[(num-1)/2] = _accompany_info2[num];
                  _accompany_info2[num] = temp;
                num = (num-1)/2;
            }else{
                break;
            }
        }
    }
    
    public int[] Dequeue(){
        var re = new int[]{_priorityqueue[0],_accompany_info[0],_accompany_info2[0]};
        var qcount = _priorityqueue.Count;
        var temp = _priorityqueue[0]; _priorityqueue[0] = _priorityqueue[qcount-1]; _priorityqueue[qcount-1] = temp;
        temp = _accompany_info[0]; _accompany_info[0] = _accompany_info[qcount-1]; _accompany_info[qcount-1] = temp;
        temp = _accompany_info2[0]; _accompany_info2[0] = _accompany_info2[qcount-1]; _accompany_info2[qcount-1] = temp;
        _priorityqueue.RemoveAt(qcount-1);
        _accompany_info.RemoveAt(qcount-1);
        _accompany_info2.RemoveAt(qcount-1);
        int num = 0;
        while(true){
            int swapnum = -1;
            if((num+1)*2 < _priorityqueue.Count){
                if(_priorityqueue[num*2+1] < _priorityqueue[(num+1)*2]){ //大小逆の時弄るとこ
                    swapnum = num*2+1;
                }else{
                    swapnum = (num+1)*2;
                }
            }else if(num*2+1 < _priorityqueue.Count){
                swapnum = num*2+1;
            }
            if(swapnum == -1) break;
            if(_priorityqueue[swapnum] < _priorityqueue[num]){ //大小逆の時弄るとこ
                temp = _priorityqueue[swapnum];_priorityqueue[swapnum] = _priorityqueue[num];_priorityqueue[num] = temp;
                temp = _accompany_info[swapnum];_accompany_info[swapnum] = _accompany_info[num];_accompany_info[num] = temp;
                temp = _accompany_info2[swapnum];_accompany_info2[swapnum] = _accompany_info2[num];_accompany_info2[num] = temp;
                num = swapnum;
            }else{
                break;
            }
        }
        return re;
    }
    
    public int[] Peek(){
        var temp = new int[]{_priorityqueue[0],_accompany_info[0],_accompany_info2[0]};
        return temp;
    }
    
    public int Count(){
        return _priorityqueue.Count;
    }
}

class Permutation{
    private int[] _permutation;
    private int _length;
    
    public Permutation(int a){
        _permutation = new int[a];
        for(int i=0;i<a;i++){
            _permutation[i] = i;
        }
        _length = a;
    }
    public int[] now(){
        return _permutation;
    }
    
    public bool next(){
        var upper = -1;
        for(int i=0;i<_length-1;i++){
            if(_permutation[i] < _permutation[i+1]) upper = i;
        }
        if(upper == -1){
            return false;
        }
        var bigger = -1;
        for(int i=upper;i<_length;i++){
            if(_permutation[upper] <= _permutation[i]) bigger = i;
        }
        var temp = _permutation[upper];
        _permutation[upper] = _permutation[bigger];
        _permutation[bigger] = temp;
        var list = new List<int>();
        upper++;
        for(int i=upper;i<_length;i++){
            list.Add(_permutation[i]);
        }
        list.Reverse();
        for(int i=upper;i<_length;i++){
            _permutation[i] = list[i-upper];
        }
        return true;
    }
    
    public void prev0(){
        Array.Reverse(_permutation);
    }
    
    public bool prev(){
        var lower = -1;
        for(int i=0;i<_length-1;i++){
            if(_permutation[i] > _permutation[i+1]) lower = i;
        }
        if(lower == -1){
            return false;
        }
        var smaller = -1;
        for(int i=lower;i<_length;i++){
            if(_permutation[lower] >= _permutation[i]) smaller = i;
        }
        var temp = _permutation[lower];
        _permutation[lower] = _permutation[smaller];
        _permutation[smaller] = temp;
        var list = new List<int>();
        lower++;
        for(int i=lower;i<_length;i++){
            list.Add(_permutation[i]);
        }
        list.Reverse();
        for(int i=lower;i<_length;i++){
            _permutation[i] = list[i-lower];
        }
        return true;
    }
}

class RMQ{
    private int[] _rmq;
    private int _number = -1;
    private int inf = 2147483647;
    
    public RMQ(int a){
        int n = 1;
        while(n < a) n*=2;
        _number = n-1;
        n = n*2-1;
        _rmq = new int[n];
    }
    
    public void Initialize(int a){
        for(int i=0;i<_rmq.Length;i++){
            _rmq[i] = a;
        }
    }
    
    public void Change(int num,int value){
        var changenum = _number + num;
        _rmq[changenum] = value;
        while(changenum > 0){
            changenum = (changenum-1)/2;
            _rmq[changenum] = Min(_rmq[changenum*2+1],_rmq[changenum*2+2]);
        }
    }
    
    public int Query(int a,int b){return act_query(a,++b,0,0,_number+1);}
    public int act_query(int a,int b,int k,int l,int r){
        if(b <= l || r <= a){
            return inf;
        }
        if(a <= l && r <= b){
            return _rmq[k];
        }
        int vl = act_query(a,b,k*2+1,l,(l+r)/2);
        int vr = act_query(a,b,k*2+2,(l+r)/2,r);
        return Min(vl,vr);
    }
}

class RMS{
    private int[] _rms;
    private int _number = -1;
    private int zero = 0;
    
    public RMS(int a){
        int n = 1;
        while(n < a) n*=2;
        _number = n-1;
        n = n*2-1;
        _rms = new int[n];
    }
    
    public void Change(int num,int value){
        var changenum = _number + num;
        _rms[changenum] = value;
        while(changenum > 0){
            changenum = (changenum-1)/2;
            _rms[changenum] = _rms[changenum*2+1] + _rms[changenum*2+2];
        }
    }
    
    public int Query(int a,int b){return act_query(a,++b,0,0,_number+1);}
    public int act_query(int a,int b,int k,int l,int r){
        if(b <= l || r <= a){
            return zero;
        }
        if(a <= l && r <= b){
            return _rms[k];
        }
        int vl = act_query(a,b,k*2+1,l,(l+r)/2);
        int vr = act_query(a,b,k*2+2,(l+r)/2,r);
        return vl + vr;
    }
    
    public void Check(){
        for(int i=0;i<_rms.Length;i++){
            WriteLine(_rms[i]);
        }
    }
}

class bitRMS{
    private int[] _rms;
    private int _number = -1;
    private int zero = 0;
    
    public bitRMS(int a){
        int n = 1;
        while(n < a) n*=2;
        _number = n-1;
        n = n*2-1;
        _rms = new int[n];
    }
    
    public void Change(int num,int value){
        var changenum = _number + num;
        _rms[changenum] = value;
        while(changenum > 0){
            changenum = (changenum-1)/2;
            _rms[changenum] = _rms[changenum*2+1] | _rms[changenum*2+2];
        }
    }
    
    public int Query(int a,int b){return act_query(a,++b,0,0,_number+1);}
    public int act_query(int a,int b,int k,int l,int r){
        if(b <= l || r <= a){
            return zero;
        }
        if(a <= l && r <= b){
            return _rms[k];
        }
        int vl = act_query(a,b,k*2+1,l,(l+r)/2);
        int vr = act_query(a,b,k*2+2,(l+r)/2,r);
        return vl | vr;
    }
    
    public void Check(){
        for(int i=0;i<_rms.Length;i++){
            WriteLine(_rms[i]);
        }
    }
}