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 (Python):
def main(sample_file = ''):

    """ convenient functions
    
    
    
    
    
    """

    """convenient decorator
    
    
        
        
        
        
        
        
        
        
        
        
    """
    
    
    import sys
    sys.setrecursionlimit(10**7)
    from itertools import accumulate, combinations, permutations, product 
    
    from math import factorial, ceil, floor, sqrt
    def factorize(n):
        """return the factors of the Arg and count of each factor
        
        Args:
            n (long): number to be resolved into factors
        
        Returns:
            list of tuples: factorize(220) returns [(2, 2), (5, 1), (11, 1)]
        """
        fct = []  
        b, e = 2, 0  
        while b * b <= n:
            while n % b == 0:
                n = n // b
                e = e + 1
            if e > 0:
                fct.append((b, e))
            b, e = b + 1, 0
        if n > 1:
            fct.append((n, 1))
        return fct
    def combinations_count(n, r):   
        """Return the number of selecting r pieces of items from n kinds of items.
        
        Args:
            n (long): number
            r (long): number
        
        Raises:
            Exception: not defined when n or r is negative
        
        Returns:
            long: number
        """
        
        if n < 0 or r < 0:
            raise Exception('combinations_count(n, r) not defined when n or r is negative')
        if n - r < r: r = n - r
        if r < 0: return 0
        if r == 0: return 1
        if r == 1: return n
        numerator = [n - r + k + 1 for k in range(r)]
        denominator = [k + 1 for k in range(r)]
        for p in range(2,r+1):
            pivot = denominator[p - 1]
            if pivot > 1:
                offset = (n - r) % p
                for k in range(p-1,r,p):
                    numerator[k - offset] /= pivot
                    denominator[k] /= pivot
        result = 1
        for k in range(r):
            if numerator[k] > 1:
                result *= int(numerator[k])
        return result
    def combinations_with_replacement_count(n, r):
        """Return the number of selecting r pieces of items from n kinds of items allowing individual elements to be repeated more than once.
        
        Args:
            n (long): number
            r (long): number
        
        Raises:
            Exception: not defined when n or r is negative
        
        Returns:
            long: number
        """
        if n < 0 or r < 0:
            raise Exception('combinations_with_replacement_count(n, r) not defined when n or r is negative')
        elif n == 0:
            return 1
        else:
            return combinations_count(n + r - 1, r)
    from bisect import bisect_left, bisect_right
    from collections import deque, Counter, defaultdict 
    from heapq import heapify, heappop, heappush, heappushpop, heapreplace,nlargest,nsmallest 
    from copy import deepcopy, copy 
    import operator
    from operator import itemgetter 
    
    
    from functools import reduce, lru_cache
    def chmin(x, y):
        """change minimum
        if x > y, x = y and return (x, True).
        convenient when solving problems of dp[i]
        
        Args:
            x (long): current minimum value
            y (long): potential minimum value
        
        Returns:
            (x, bool): (x, True) when updated, else (x, False)
        """
        if x > y:
            x = y
            return (x, True)
        else:
            return (x, False)
    def chmax(x, y):
        """change maximum
        if x < y, x = y and return (x, True).
        convenient when solving problems of dp[i]
        
        Args:
            x (long): current maximum value
            y (long): potential maximum value
        
        Returns:
            (x, bool): (x, True) when updated, else (x, False)
        """
        if x < y:
            x = y
            return (x, True)
        else:
            return (x, False)

    from fractions import gcd 
    def gcds(numbers):
        return reduce(gcd, numbers)
    def lcm(x, y):
        return (x * y) // gcd(x, y)
    def lcms(numbers):
        return reduce(lcm, numbers, 1)
    def make_divisors(n, reversed=False):
        """create list of divisors
        
        Args:
            number (int): number from which list of divisors is created
            reversed (bool, optional): ascending order if False. Defaults to False.
        
        Returns:
            list: list of divisors
        """
        divisors = set()
        for i in range(1, int(n**0.5)+1):
            if n % i == 0:
                divisors.add(i)
                divisors.add(n//i)
        return sorted(list(divisors),reverse=reversed)
    
    
    
    INF = 10 ** 18
    MOD = 10 ** 9 + 7
    AtoZ = list('abcdefghijklmnopqrsruvwxyz') 
    modpow = lambda a, n, p = MOD: pow(a, n, p) 
    def modinv(a, p = MOD):
        
        
        return modpow(a, p-2, p)
    def modinv_list(n, p = MOD):
        if n <= 1:
            return [0,1][:n+1]
        else:
            inv_t = [0,1]
            for i in range(2, n+1):
                inv_t += [inv_t[p % i] * (p - int(p / i)) % p]
            return inv_t
    def modfactorial_list(n, p = MOD):
        if n == 0:
            return [1]
        else:
            l = [0] * (n+1)
            tmp = 1
            for i in range(1, n+1):
                tmp = tmp * i % p
                l[i] = tmp
            return l
    def modcomb(n, k, fac_list = [], p = MOD):
        
        
        from math import factorial
        if n < 0 or k < 0 or n < k: return 0
        if n == 0 or k == 0: return 1
        if len(fac_list) <= n:
            a = factorial(n) % p
            b = factorial(k) % p
            c = factorial(n-k) % p
        else:
            a = fac_list[n]
            b = fac_list[k]
            c = fac_list[n-k]
        return (a * modpow(b, p-2, p) * modpow(c, p-2, p)) % p
    def modadd(a, b, p = MOD):
        return (a + b) % MOD
    def modsub(a, b, p = MOD):
        return (a - b) % p
    def modmul(a, b, p = MOD):
        return ((a % p) * (b % p)) % p
    def moddiv(a, b, p = MOD):
        return modmul(a, modpow(b, p-2, p))

    class UnionFindTree:
        """union find tree class
        TODO: fix this description...
        how to use (example):
        >>  uf = UnionFindTree(N) 
        >>  if uf.find_root(a) == uf.find_root(b):
        >>      do something
        >>  else:
        >>      do something
        >>      uf.unite(a, b)
        """
        def __init__(self, N):
            self.root = [-1] * (N+1)
            self.rank   = [0]  * (N+1)
            self.connected_num = [1] * (N+1)
    
        def find_root(self,x):
            root = self.root
            while root[x] != -1:
                x = root[x]
            return x
    
        def unite(self,x,y):
            root = self.root
            rank = self.rank
            connected_num = self.connected_num
            find_root = self.find_root
    
            rx = find_root(x)
            ry = find_root(y)
            if rx != ry:
                if rank[rx] < rank[ry]:
                    root[rx] = ry
                    rx,ry = ry,rx
                else:
                    if rank[rx] == rank[ry]:
                        rank[rx] += 1
                    root[ry] = rx       
                connected_num[rx] += connected_num[ry]

    
    
    
    
    
    
    
    

    def BellmanFord(N, M, ABC, vertex_start, vertex_end, value_if_inf = -1, find_shortest = False):
        """to calculate furthest or shortest length between vertex_start and vertex_end using BellmanFord algorithm
        
        Args:
            N (int): number of vertices
            M (int): number of edges
            ABC (list): [(ai, bi, ci) for _ in range(N)] where i-th edge is directed from vertex ai to vertex bi and the length is ci 
            vertex_start (int): start vertex. usually use 0.
            vertex_end (int): end vertex. usually use N-1.
            value_if_inf (int or string as you like, optional): value you want when the furthest (or shortest) distance is infinite (or -infinite). Defaults to -1.
            find_shortest (bool, optional): choose False to find furthest path. Defaults to False.
        
        Returns:
            int or string: normally int (but can be str if you set value_if_inf to str)
            
        Example:
                N, M, P = R()
                ABC = [R() for _ in range(M)]
                ABC = [(a-1, b-1, c-P) for a, b, c in ABC]
                print(BellmanFord(N, M, ABC, 0, N-1, value_if_inf = 'inf'))

        """

        def make_reachable_list(N, M, ABC, vertex_start, vertex_end):
            reachable_to_direct = defaultdict(list)
            reachable_from_direct = defaultdict(list)
            reachable_from_start = [False] * N
            reachable_to_end = [False] * N
            reachable_from_start[vertex_start] = True
            reachable_to_end[vertex_end] = True
            reachable_from_both_sides = [False] * N
            dfs_from_start = []
            dfs_to_end = []
            for a, b, c in ABC:
                reachable_to_direct[a].append(b)
                reachable_from_direct[b].append(a)
                if a == vertex_start:
                    dfs_from_start.append(b)
                    reachable_from_start[b] = True
                if b == vertex_end:
                    dfs_to_end.append(a)
                    reachable_to_end[a] = True
            while dfs_from_start:
                v = dfs_from_start.pop()
                for i in reachable_to_direct[v]:
                    if not reachable_from_start[i]:
                        reachable_from_start[i] = True
                        dfs_from_start.append(i)
            while dfs_to_end:
                v = dfs_to_end.pop()
                for i in reachable_from_direct[v]:
                    if not reachable_to_end[i]:
                        reachable_to_end[i] = True
                        dfs_to_end.append(i)
            for i in range(N):
                reachable_from_both_sides[i] = reachable_from_start[i] and reachable_to_end[i]
            return reachable_from_both_sides
        
        reachable_from_both_sides = make_reachable_list(N, M, ABC, vertex_start, vertex_end)
        
        if find_shortest:
            dist = [INF for i in range(N)]
        else:
            dist = [-INF for i in range(N)]
        
        dist[vertex_start] = 0
        for i in range(N):
            updated = False
            for a, b, c in ABC:
                if not reachable_from_both_sides[a]:
                    continue
                elif find_shortest:
                    update_condition = dist[a] + c < dist[b]
                else:
                    update_condition = dist[a] + c > dist[b]
                if dist[a] != INF and update_condition:
                    dist[b] = dist[a] + c
                    updated = True
                    if i == N-1:
                        return value_if_inf
            if not updated:
                break
        return dist[vertex_end]

    
    def warshall_floyd(number_vertex, XYD, shift_one_for_vertex=False):
        
        
        
        
        
        d = [[float("inf")]*number_vertex for i in range(number_vertex)]
        for x, y, dist in XYD:
            if shift_one_for_vertex:
                x = x - 1
                y = y - 1
            d[x][y] = dist
            d[y][x] = dist
        for i in range(number_vertex):
            d[i][i] = 0 
        for k in range(number_vertex):
            for i in range(number_vertex):
                for j in range(number_vertex):
                    d[i][j] = min(d[i][j],d[i][k] + d[k][j])
        return d


    """ initialize variables and set inputs
    
        
        
            
            
    
        
        
        
        
        
        
        
    
        
        
        
        
    
        
        
    """

    
    r = lambda: sys.stdin.readline().strip()
    r_int = lambda: int(r())
    r_float = lambda: float(r())
    R = lambda: list(map(int, r().split()))
    R_str = lambda: r().split()
    R_map = lambda: map(int, r().split())
    R_float = lambda: list(map(float, r().split()))
    R_tuple = lambda: tuple(map(int, r().split()))

    """ how to treat input
    
    
    
    
    
    
    
    """

    
    if sample_file:
        sys.stdin = open(sample_file)
        
    
    
    
    N = r_int()
    S = r()
    Q = r_int()
    Que = [R_str() for _ in range(Q)]
    
    
    class SegTree:
        """
        ref: https://qiita.com/takayg1/items/c811bd07c21923d7ec69
        init(init_val, ide_ele): 配列init_valで初期化 O(N)
        update(k, x): k番目の値をxに更新 O(logN)
        query(l, r): 区間[l, r)をsegfuncしたものを返す O(logN)
        """
        def __init__(self, init_val, segfunc, ide_ele):
            """
            init_val: 配列の初期値
            segfunc: 区間にしたい操作
            ide_ele: 単位元
            n: 要素数
            num: n以上の最小の2のべき乗
            tree: セグメント木(1-index)
            """
            n = len(init_val)
            self.segfunc = segfunc
            self.ide_ele = ide_ele
            self.num = 1 << (n - 1).bit_length()
            self.tree = [ide_ele] * 2 * self.num
            
            for i in range(n):
                self.tree[self.num + i] = init_val[i]
            
            for i in range(self.num - 1, 0, -1):
                self.tree[i] = self.segfunc(self.tree[2 * i], self.tree[2 * i + 1])

        def update(self, k, x):
            """
            k番目の値をxに更新
            k: index(0-index)
            x: update value
            """
            k += self.num
            self.tree[k] = x
            while k > 1:
                self.tree[k >> 1] = self.segfunc(self.tree[k], self.tree[k ^ 1])
                k >>= 1

        def query(self, l, r):
            """
            [l, r)のsegfuncしたものを得る
            l: index(0-index)
            r: index(0-index)
            """
            res = self.ide_ele

            l += self.num
            r += self.num
            while l < r:
                if l & 1:
                    res = self.segfunc(res, self.tree[l])
                    l += 1
                if r & 1:
                    res = self.segfunc(res, self.tree[r - 1])
                l >>= 1
                r >>= 1
            return res
    
    
    
    def segfunc(x, y):
        return x | y
    
    def count_ones_by_bitmask(num):
        count = 0
        while num:
            count += num & 1
            num >>= 1
        return count
    
    S_int = [2**(ord(i)-97) for i in S]
    ide_ele = 0
    seg = SegTree(S_int, segfunc, ide_ele)
    for i, a, b in Que:
        if i == '1':
            seg.update(int(a)-1, 2**(ord(b)-97))
        else:
            print(count_ones_by_bitmask(seg.query(int(a)-1, int(b))))

    
    
    

    """memo: how to use defaultdict of list
    
    Dic = defaultdict(list)
    
    Dic[x].append(y)
    
    for k, v in Dic.items():
    """
    
    """memo: how to solve binary problems
    
    >>> a = 5
    >>> bin_str_a = format(a, '
    >>> print(bin_str_a)
    0b0101 
    """
    
    """memo: how to solve the problem
    creating simple test/answer
    greed
    simple dp
    graph
    """

if __name__ == '__main__':
    main()

Solution (Python):
class SegmentTree:
    def __init__(self,siz,v = 0):
        self.n = 1
        self.v = v
        while self.n < siz: self.n *= 2
        self.node = [self.v]*(2*self.n-1)

    def merge(self,x,y): return x | y

    def update(self,i,x):
        i += self.n-1
        self.node[i] = x
        while i > 0:
            i = (i-1)//2
            self.node[i] = self.merge(self.node[i*2+1],self.node[i*2+2])
    
    def query(self,a,b):
        vl = vr = self.v
        a += self.n-1
        b += self.n-1
        while a < b:
            if a & 1 == 0: vl = self.merge(vl,self.node[a])
            if b & 1 == 0: vr = self.merge(vr,self.node[b-1])
            a //= 2
            b = (b-1)//2
        return self.merge(vl,vr)
    
n = int(input())
st = SegmentTree(n)
s = list(input())
def f(c): return 1<<(ord(c) - ord("a"))
for i in range(n): st.update(i,f(s[i]))
q = int(input())
for _ in range(q):
    typ,x,y = input().split()
    if typ == "1":
        i,c = int(x)-1,y
        if s[i] == c: continue
        st.update(i,f(c))
        s[i] = c
    else:
        l,r = int(x)-1,int(y)
        print(bin(st.query(l,r)).count("1"))

Solution (Python):
import sys
from bisect import bisect_left, bisect_right, insort

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))

N = ir()
S = list('-' + sr())
d = [[] for _ in range(26)]
for i in range(1, N+1):
    s = S[i]
    o = ord(s) - ord('a')
    d[o].append(i)

Q = ir()
for _ in range(Q):
    q, a, b = sr().split()
    if q == '1':
        a = int(a)
        if S[a] == b:
            continue
        prev = ord(S[a]) - ord('a')
        d[prev].pop(bisect_left(d[prev], a))
        next = ord(b) - ord('a')
        insort(d[next], a)
        S[a] = b
    else:
        left = int(a); right = int(b)
        ans = 0
        for alpha in range(26):
            index = bisect_left(d[alpha], left)
            if index < len(d[alpha]) and d[alpha][index] <= right:
                ans += 1
        print(ans)

Solution (Python):
class SegmentTree:
    def __init__(self,n):
        self.siz = 1
        while self.siz < n: self.siz *= 2
        self.node = [0]*(2*self.siz-1)

    def update(self,i,x):
        i += self.siz-1
        self.node[i] = x
        while i > 0:
            i = (i-1)//2
            self.node[i] = self.node[i*2+1] | self.node[i*2+2]
    
    def query(self,a,b,k=0,l=0,r=-1):
        if r < 0: r = self.siz
        if r <= a or b <= l: return 0
        if a <= l and r <= b: return self.node[k]
        vl = self.query(a,b,k*2+1,l,(l+r)//2)
        vr = self.query(a,b,k*2+2,(l+r)//2,r)
        return vl | vr
    
n = int(input())
st = SegmentTree(n)
s = list(input())
def f(c): return 1<<(ord(c) - ord("a"))
for i in range(n): st.update(i,f(s[i]))
q = int(input())
for _ in range(q):
    typ,x,y = input().split()
    if typ == "1":
        i,c = int(x)-1,y
        if s[i] == c: continue
        st.update(i,f(c))
        s[i] = c
    else:
        l,r = int(x)-1,int(y)
        print(bin(st.query(l,r)).count("1"))

Solution (Python):
import bisect
import sys
input = lambda: sys.stdin.readline().rstrip()

n=int(input())
s= list(input())
q=[]
qq=int(input())
for i in range(qq):
    q.append(list(input().split()))


x=[[] for i in range(26)]
for i,j in enumerate(s):
    x[ord(j)-97].append(i)


for i in range(26):
    x[i].append(5*10**5)


for i,j,k in q:
    if int(i)==1:
        if s[int(j)-1]!=k:
            v=s[int(j)-1]
            s[int(j)-1]=k
            
            index=bisect.bisect_right(x[ord(v)-97], int(j)-1) - 1
            x[ord(v)-97].pop(index)
            
            bisect.insort_right(x[ord(k)-97],int(j)-1)
    else:
        cnt=0
        j=int(j)-1
        k=int(k)-1
        for l in range(26):
            index=bisect.bisect_left(x[l],j)
            if x[l][index]<=k:
                cnt+=1


        print(cnt)

Solution (Python):
f=input; n=int(f()); s=list(f())
d={chr(97+i):[0]*(n+1) for i in range(26)}
def bsum(k,i):
  s=0
  while i: s+=d[k][i]; i-=i&-i
  return s
def badd(k,i,x):
  while i<=n: d[k][i]+=x; i+=i&-i
for i in range(n): badd(s[i],i+1,1)
for i in range(int(f())):
  a,b,c=f().split(); b=int(b)-1
  if a>'1': print(sum(1 for k in d.keys() if bsum(k,int(c))-bsum(k,b)))
  else: badd(s[b],b+1,-1); s[b]=c; badd(c,b+1,1)

Solution (Python):
f=input; from bisect import bisect_left as g, insort as h
d={chr(97+i):[] for i in range(26)}
f(); s,i=list(f()),0
for c in s: d[c]+=[i]; i+=1
for _ in range(int(f())):
  a,b,c=f().split(); b=int(b)-1
  if a>'1': print(sum(1 for l in d.values() if g(l,b)<len(l) and l[g(l,b)]<int(c)))
  elif s[b]!=c: l=d[s[b]]; l.pop(g(l,b)); s[b]=c; h(d[c],b)

Solution (Python):
f=input; from bisect import bisect_left as g, insort as h
f(); s,i=list(f()),0
from collections import *
d=defaultdict(list)
for c in s: d[c]+=[i]; i+=1
for _ in range(int(f())):
  a,b,c=f().split(); b=int(b)-1
  if a>'1': print(sum(1 for l in d.values() if g(l,b)<len(l) and l[g(l,b)]<int(c)))
  elif s[b]!=c: l=d[s[b]]; l.pop(g(l,b)); s[b]=c; h(d[c],b)

Solution (Python):
f=input
from bisect import bisect_left as g, insort as h
n,s=int(f()),list(f())
d={chr(97+i):[] for i in range(26)}
for i in range(n): d[s[i]]+=[i]
for _ in range(int(f())):
  a,b,c=f().split(); b=int(b)-1
  if a>'1': print(sum(1 for l in d.values() if g(l,b)<len(l) and l[g(l,b)]<int(c)))
  elif s[b]!=c: l=d[s[b]]; l.pop(g(l,b)); s[b]=c; h(d[c],b)

Solution (Python):
f=input
from bisect import bisect_left as g, insort as h
n,s=int(f()),list(f())
d={chr(97+i):[] for i in range(26)}
for i in range(n): d[s[i]]+=[i]
for _ in range(int(f())):
  a,b,c=f().split(); b=int(b)-1
  if a>'1': print(sum(1 for l in d.values() if g(l,b)<len(l) and l[g(l,b)]<int(c)))
  elif s[b]!=c: l=d[s[b]]; l.pop(g(l,b)); s[b]=c; h(d[c],b)

Solution (Python):
f=input
n,s,q=int(f()),list(f()),int(f())
d={chr(97+i):[] for i in range(26)}
for i in range(n):
  d[s[i]]+=[i]
from bisect import *
for i in range(q):
  a,b,c=f().split()
  b=int(b)-1
  if a=='1':
    if s[b]==c: continue
    d[s[b]].pop(bisect(d[s[b]],b)-1)
    s[b]=c
    insort(d[c],b)
  else:
    t=0
    for l in d.values():
      m=bisect(l,b-1)
      if m<len(l) and l[m]<int(c): t+=1
    print(t)

Solution (Python):
f=input
n,l,q=int(f()),list(f()),int(f())
B=[[0]*-~n for i in range(26)]
def S(o,i):
  s=0
  while i: s+=B[o][i]; i-=i&-i
  return s
def A(o,i,x):
  while i<=n: B[o][i]+=x; i+=i&-i
for i in range(n): A(ord(l[i])-97,i+1,1)
for i in range(q):
  a,b,c=f().split(); b=int(b)
  if a>'1': print(sum(1 for o in range(26) if S(o,int(c))-S(o,b-1)))
  else: A(ord(l[b-1])-97,b,-1); l[b-1]=c; A(ord(c)-97,b,1)

Solution (Python):
f=input;n,l,q=int(f()),list(f()),int(f())
B=[[0]*-~n for i in range(26)]
def S(o,i):
  s=0
  while i: s+=B[o][i]; i-=i&-i
  return s
def A(o,i,x):
  while i<=n: B[o][i]+=x; i+=i&-i
for i in range(n): A(ord(l[i])-97,i+1,1)
for i in range(q):
  a,b,c=input().split(); b=int(b)
  if a>'1': print(sum(1 for o in range(26) if S(o,int(c))-S(o,b-1)))
  else: A(ord(l[b-1])-97,b,-1); l[b-1]=c; A(ord(c)-97,b,1)

Solution (Python):
n=int(input())
l=list(input())
q=int(input())
bit=[[0]*(n+1) for i in range(26)]
def bit_sum(o,i):
  s=0
  while i:
    s+=bit[o][i]
    i-=i&-i
  return s
def bit_add(o,i,x):
  while i<=n:
    bit[o][i] += x
    i+=i&-i
for i in range(n):
  bit_add(ord(l[i])-97,i+1,1)
for i in range(q):
  a,b,c=input().split()
  b=int(b)-1
  if a=='1':
    bit_add(ord(l[b])-97,b+1,-1)
    l[b]=c
    bit_add(ord(c)-97,b+1,1)
  else:
    c=int(c)
    print(sum(1 for o in range(26) if bit_sum(o,c)-bit_sum(o,b)))

Solution (Python):
import sys
from bisect import bisect_left, bisect_right, insort

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))

N = ir()
S = list('-' + sr())
d = [[] for _ in range(26)]
for i in range(1, N+1):
    s = S[i]
    o = ord(s) - ord('a')
    d[o].append(i)

Q = ir()
for _ in range(Q):
    q, a, b = sr().split()
    if q == '1':
        a = int(a)
        if S[a] == b:
            continue
        prev = ord(S[a]) - ord('a')
        d[prev].pop(bisect_left(d[prev], a))
        next = ord(b) - ord('a')
        insort(d[next], a)
        S[a] = b
    else:
        a = int(a); b = int(b)
        ans = 0
        for alpha in range(26):
            if bisect_right(d[alpha], b) - bisect_left(d[alpha], a) >= 1:
                ans += 1
        print(ans)

Solution (Python):
import sys
from bisect import bisect_left, bisect_right, insort

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))

N = ir()
S = list('-' + sr())
d = [[] for _ in range(26)]
for i in range(1, N+1):
    s = S[i]
    o = ord(s) - ord('a')
    d[o].append(i)

Q = ir()
for _ in range(Q):
    q, a, b = sr().split()
    if q == '1':
        a = int(a)
        if S[a] == b:
            continue
        prev = ord(S[a]) - ord('a')
        d[prev].pop(bisect_left(d[prev], a))
        next = ord(b) - ord('a')
        insort(d[next], a)
        S[a] = b
    else:
        a = int(a); b = int(b)
        ans = 0
        for alpha in range(26):
            if bisect_right(d[alpha], b) - bisect_left(d[alpha], a) >= 1:
                ans += 1
        print(ans)

Solution (Python):
import sys
from bisect import bisect_left, bisect_right, insort

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))

N = ir()
S = list('-' + sr())
d = [[] for _ in range(26)]
for i in range(1, N+1):
    s = S[i]
    o = ord(s) - ord('a')
    d[o].append(i)

Q = ir()
for _ in range(Q):
    q, a, b = sr().split()
    if q == '1':
        a = int(a)
        if S[a] == b:
            continue
        prev = ord(S[a]) - ord('a')
        d[prev].remove(a)
        next = ord(b) - ord('a')
        insort(d[next], a)
        S[a] = b
    else:
        a = int(a); b = int(b)
        ans = 0
        for alpha in range(26):
            if bisect_right(d[alpha], b) - bisect_left(d[alpha], a) >= 1:
                ans += 1
        print(ans)

Solution (Python):

import sys
from bisect import bisect_left, bisect_right, insort_left
from collections import defaultdict

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))


N = ir()
S = list(sr())
dic = defaultdict(list)
for i, s in enumerate(S):
    dic[s].append(i)

Q = ir()
for _ in range(Q):
    a, b, c = sr().split()
    if a == '1':
        b = int(b) - 1
        if S[b] == c:
            continue
        dic[S[b]].remove(b)
        insort_left(dic[c], b)
        S[b] = c
    else:
        b = int(b) - 1; c = int(c) - 1
        kind = 0
        for x in range(26):
            word = chr(ord('a')+x)
            if len(dic[word]) == 0:
                continue
            i = bisect_left(dic[word], b)
            j = bisect_right(dic[word], c)
            if i != j:
                kind += 1
        print(kind)

Solution (Python):
import sys
sys.setrecursionlimit(10**6) 
import math
from copy import copy, deepcopy
from operator import itemgetter
from bisect import bisect_left, bisect, bisect_right

from collections import deque 


from collections import Counter

from itertools import accumulate

from heapq import heapify,heappop,heappush



def input(): return sys.stdin.readline()[:-1]
def printl(li): print(*li, sep="\n")
def argsort(s, return_sorted=False): 
    inds=sorted(range(len(s)), key=lambda k: s[k])
    if return_sorted: return inds, [s[i] for i in inds]
    return inds

class segtree():
    def __init__(self,A,ide=0):
        n=len(A)
        num=2**(n-1).bit_length()
        seg=[ide]*(2*num-1)
        segfunc=self.segfunc
        self.ide,self.n,self.num,self.seg = ide, n, num, seg
        for i in range(n): seg[i+num-1]=A[i]
        for i in range(num-2,-1,-1):seg[i]=segfunc(seg[2*i+1],seg[2*i+2])
    
    def segfunc(self,x,y):return x|y 
    
    def update(self,k,x):
        k += self.num-1
        seg,segfunc=self.seg,self.segfunc
        seg[k] = x
        while k:
            k = (k-1)//2
            seg[k] = segfunc(seg[k*2+1],seg[k*2+2])
    
    def query(self,p,q):
        if q<=p: return self.ide
        num,segfunc,seg=self.num,self.segfunc,self.seg
        p += num-1; q += num-2
        res=self.ide
        while q-p>1:
            if p&1 == 0: res = segfunc(res,seg[p])
            if q&1 == 1:
                res = segfunc(res,seg[q])
                q -= 1
            p,q = p//2, (q-1)//2
        if p == q: res = segfunc(res,seg[p])
        else: res = segfunc(segfunc(res,seg[p]),seg[q])
        return res 

def main():
    mod = 10**9+7
    alpha2num = lambda c: 2**(ord(c) - ord('a'))
    

    N = int(input())
    S=input()
    
    
    
    
    A=list(map(alpha2num, list(S)))
    
    
    seg=segtree(A)
    
    Q=int(input())
    for i in range(Q):
        t, a,b =input().split()
        if t=='1':
            a=int(a)
            seg.update(a-1,alpha2num(b))
        else:
            a,b=int(a),int(b)
            x=seg.query(a-1,b)
            count=0
            for i in range(26):
                count+= (x>>i & 1)
            print(count)






if __name__ == "__main__":
    main()

Solution (Python):



class BIT:
    def __init__(self,n):
        self.n=n
        self.data=[0]*(n+1)
    def to_sum(self,i):
        s=0     
        while i>0:
            s+=self.data[i]
            i-=(i& -i)
        return s
    def add(self,i,x):
        while i<=self.n:
            self.data[i]+=x
            i+=(i & -i)
    def get(self,i,j):
        return self.to_sum(j)-self.to_sum(i-1)
n=int(input())
s=list(input())
q=int(input())
que=[]

for i in range(q):
    p=list(input().split())
    que.append(p)
alpha="abcdefghijklmnopqrstuvwxyz"
segtree={alpha[i]:BIT(n) for i in range(26)}  
for i in range(n):
    segtree[s[i]].add(i+1,1)
for q in que:
    x,y,z=q[0],q[1],q[2]
    if int(x)==1:
        
        y=int(y)  
        for i in range(26):
            if segtree[alpha[i]].get(y,y)==1:
                segtree[alpha[i]].add(y,-1)
                break
        segtree[z].add(y,1)
    else:
        ans=0
        for i in range(26):
            if segtree[alpha[i]].get(int(y),int(z))>0:
                ans+=1
        print(ans)