Buggy python submission (verdict: Time Limit Exceeded):

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [set() for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1].add(l[i])
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return set()
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, set([ql[i][2]]))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(len(r))

Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

w = 800
sl = []
dl = []
for i in range((n+w-1)//w):
    ss = s[i*w:min((i+1)*w,n)]
    dl.append(set(ss))
    sl.append(ss)
if len(dl)%2==1:
    dl.append(set())
dl2 = []
for i in range(len(dl)//2):
    dl2.append(dl[2*i] | dl[2*i+1])
for i in range(q):
    if ql[i][0]=="1":
        idx = int(ql[i][1])-1
        c = ql[i][2]

        ss = sl[idx//w]
        ss[idx%w] = c
        s[idx] = c
        sl[idx//w] = ss
        dl[idx//w] = set(ss)
        if (idx//w)%2==0:
            dl2[idx//w//2] = dl[idx//w] | dl[idx//w+1]
        else:
            dl2[idx//w//2] = dl[idx//w-1] | dl[idx//w]
    else:
        l = int(ql[i][1])-1
        r = int(ql[i][2])-1

        li = l//w
        ri = r//w
        if abs(li-ri)<2:
            print(len(set(s[l:r+1])))
        else:
            u = set(sl[li][l%w:])
            u |= set(sl[ri][:r%w+1])
            if (li+1)%2==1:
                u |= dl[li+1]
                li += 1
            if (ri-1)%2==0:
                u |= dl[ri-1]
                ri -= 1
            for j in range(li+1,ri,2):
                u |= dl2[j//2]
            print(len(u))


Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

w = 800
sl = []
dl = []
for i in range((n+w-1)//w):
    ss = s[i*w:min((i+1)*w,n)]
    dl.append(set(ss))
    sl.append(ss)
if len(dl)%2==1:
    dl.append(set())
dl2 = []
for i in range(len(dl)//2):
    dl2.append(dl[2*i] | dl[2*i+1])
for i in range(q):
    if ql[i][0]=="1":
        idx = int(ql[i][1])-1
        c = ql[i][2]

        ss = sl[idx//w]
        ss[idx%w] = c
        s[idx] = c
        sl[idx//w] = ss
        dl[idx//w] = set(ss)
        if (idx//w)%2==0:
            dl2[idx//w//2] = dl[idx//w] | dl[idx//w+1]
        else:
            dl2[idx//w//2] = dl[idx//w-1] | dl[idx//w]
    else:
        l = int(ql[i][1])-1
        r = int(ql[i][2])-1

        li = l//w
        ri = r//w
        if abs(li-ri)<2:
            print(len(set(s[l:r+1])))
        else:
            u = set(sl[li][l%w:])
            u |= set(sl[ri][:r%w+1])
            if (li+1)%2==1:
                u |= dl[li+1]
                li += 1
            if (ri-1)%2==0:
                u |= dl[ri-1]
                ri -= 1
            for j in range(li+1,ri,2):
                u |= dl2[j//2]
            print(len(u))


Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

w = 800
sl = []
dl = []
for i in range((n+w-1)//w):
    ss = s[i*w:min((i+1)*w,n)]
    dl.append(set(ss))
    sl.append(ss)
if len(dl)%2==1:
    dl.append(set())
dl2 = []
for i in range(len(dl)//2):
    dl2.append(dl[2*i] | dl[2*i+1])
for i in range(q):
    if ql[i][0]=="1":
        idx = int(ql[i][1])-1
        c = ql[i][2]

        ss = sl[idx//w]
        ss[idx%w] = c
        s[idx] = c
        sl[idx//w] = ss
        dl[idx//w] = set(ss)
        if (idx//w)%2==0:
            dl2[idx//w//2] = dl[idx//w] | dl[idx//w+1]
        else:
            dl2[idx//w//2] = dl[idx//w-1] | dl[idx//w]
    else:
        l = int(ql[i][1])-1
        r = int(ql[i][2])-1

        li = l//w
        ri = r//w
        if abs(li-ri)<2:
            print(len(set(s[l:r+1])))
        else:
            u = set(sl[li][l%w:])
            u = u | set(sl[ri][:r%w+1])
            if (li+1)%2==1:
                u = u | dl[li+1]
                li += 1
            if (ri-1)%2==0:
                u = u | dl[ri-1]
                ri -= 1
            for j in range(li+1,ri,2):
                u = u | dl2[j//2]
            print(len(u))


Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

w = 800
sl = []
dl = []
for i in range((n+w-1)//w):
    ss = s[i*w:min((i+1)*w,n)]
    dl.append(set(ss))
    sl.append(ss)
if len(dl)%2==1:
    dl.append(set())
dl2 = []
for i in range(len(dl)//2):
    dl2.append(dl[2*i] | dl[2*i+1])
for i in range(q):
    if ql[i][0]=="1":
        idx = int(ql[i][1])-1
        c = ql[i][2]

        ss = sl[idx//w]
        ss[idx%w] = c
        s[idx] = c
        sl[idx//w] = ss
        dl[idx//w] = set(ss)
        if (idx//w)%2==0:
            dl2[idx//w//2] = dl[idx//w] | dl[idx//w+1]
        else:
            dl2[idx//w//2] = dl[idx//w-1] | dl[idx//w]
    else:
        l = int(ql[i][1])-1
        r = int(ql[i][2])-1

        li = l//w
        ri = r//w
        if abs(li-ri)<2:
            print(len(set(s[l:r+1])))
        else:
            u = set(sl[li][l%w:])
            u = u | set(sl[ri][:r%w+1])
            if (li+1)%2==1:
                u = u | dl[li+1]
                li += 1
            if (ri-1)%2==0:
                u = u | dl[ri-1]
                ri -= 1
            for j in range(li+1,ri,2):
                u = u | dl2[j]
            print(len(u))


Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

w = 800
sl = []
dl = []
for i in range((n+w-1)//w):
    ss = s[i*w:min((i+1)*w,n)]
    dl.append(set(ss))
    sl.append(ss)

for i in range(q):
    if ql[i][0]=="1":
        idx = int(ql[i][1])-1
        c = ql[i][2]

        ss = sl[idx//w]
        ss[idx%w] = c
        s[idx] = c
        sl[idx//w] = ss
        dl[idx//w] = set(ss)
    else:
        l = int(ql[i][1])-1
        r = int(ql[i][2])-1

        li = l//w
        ri = r//w
        if abs(li-ri)<2:
            print(len(set(s[l:r+1])))
        else:
            u = set()
            u = u | set(sl[li][l%w:])
            for j in range(li+1,ri):
                u = u | dl[j]
            u = u | set(sl[ri][:r%w+1])
            print(len(u))


Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict

n = int(input())
s = list(input())
q = int(input())
ql = [input().split() for _ in range(q)]

w = 800
sl = []
dl = []
for i in range((n+w-1)//w):
    ss = s[i*w:min((i+1)*w,n)]
    dl.append(set(ss))
    sl.append(ss)

for i in range(q):
    if ql[i][0]=="1":
        idx = int(ql[i][1])-1
        c = ql[i][2]

        ss = sl[idx//w]
        ss[idx%w] = c
        s[idx] = c
        sl[idx//w] = ss
        dl[idx//w] = set(ss)
    else:
        l = int(ql[i][1])-1
        r = int(ql[i][2])-1

        li = l//w
        ri = r//w
        if abs(li-ri)<2:
            print(len(set(s[l:r+1])))
        else:
            u = set()
            u = u | set(sl[li][l%w:])
            for j in range(li+1,ri):
                u = u | dl[j]
            u = u | set(sl[ri][:r%w+1])
            print(len(u))


Fixed submission:

class SegTree(object):
    """docstring for SegTree."""
    def __init__(self, l, _n):
        n = 1
        while n<_n:
            n *= 2
        self.n = n
        self.dat = [0 for _ in range(2*n)]
        for i in range(_n):
            self.dat[i+n-1] |= 1<<l[i]
        self.init(0)

    def init(self, i):
        if i>=self.n-1:
            return self.dat[i]
        self.dat[i] = self.init(self.left(i)) | self.init(self.right(i))
        return self.dat[i]

    def par(self, i):
        return (i-1)//2

    def left(self, i):
        return 2*i+1

    def right(self, i):
        return 2*i+2

    def update(self, i, x):
        i += self.n-1
        self.dat[i] = 1<<x
        while i>0:
            i = self.par(i)
            self.dat[i] = self.dat[self.left(i)] | self.dat[self.right(i)]

    def q(self,a,b,k,l,r):
        if r<=a or b<=l:
            return 0
        if a<=l and r<=b:
            return self.dat[k]
        return self.q(a,b,self.left(k),l,(l+r)//2) | self.q(a,b,self.right(k),(l+r)//2,r)

    def query(self,a,b):
        return self.q(a,b,0,0,self.n)

n = int(input())
s = [ord(c)-ord("a") for c in input()]
q = int(input())
ql = [input().split() for _ in range(q)]

seg = SegTree(s,n)

for i in range(q):
    if ql[i][0]=="1":
        seg.update(int(ql[i][1])-1, ord(ql[i][2])-ord("a"))
    else:
        r = seg.query(int(ql[i][1])-1, int(ql[i][2]))
        print(bin(r).count("1"))