Problem:
 Score : 700 points    Problem Statement There are N stones arranged in a row. The i -th stone from the left is painted in the color C_i .  Snuke will perform the following operation zero or more times:   Choose two stones painted in the same color. Repaint all the stones between them, with the color of the chosen stones.   Find the number of possible final sequences of colors of the stones, modulo 10^9+7 .      Constraints  1 \leq N \leq 2\times 10^5  1 \leq C_i \leq 2\times 10^5(1\leq i\leq N)  All values in input are integers.         Input Input is given from Standard Input in the following format:  N  C_1  :  C_N       Output Print the number of possible final sequences of colors of the stones, modulo 10^9+7 .        Sample Input 1 5
1
2
1
2
2      Sample Output 1 3  We can make three sequences of colors of stones, as follows:   (1,2,1,2,2) , by doing nothing.  (1,1,1,2,2) , by choosing the first and third stones to perform the operation.  (1,2,2,2,2) , by choosing the second and fourth stones to perform the operation.        Sample Input 2 6
4
2
5
4
2
4      Sample Output 2 5       Sample Input 3 7
1
3
1
2
3
3
2      Sample Output 3 5

Solution (Python):
import sys
from collections import defaultdict

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

in_n = lambda: int(readline())
in_nn = lambda: map(int, readline().split())
in_s = lambda: readline().rstrip().decode('utf-8')
in_nl = lambda: list(map(int, readline().split()))
in_nl2 = lambda H: [in_nl() for _ in range(H)]
in_map = lambda: [s == ord('.') for s in readline() if s != ord('\n')]
in_map2 = lambda H: [in_map() for _ in range(H)]
in_all = lambda: map(int, read().split())


def main():

    N = in_n()
    C = list(in_all())

    mod = 10**9 + 7

    d = defaultdict(lambda: -1)
    d[C[0]] = 0
    dp = [0] * N
    dp[0] = 1

    for i in range(1, N):
        j = d[C[i]]
        if j == -1:
            dp[i] = dp[i - 1]
        elif j == i - 1:
            dp[i] = dp[i - 1]
        else:
            dp[i] = dp[i - 1] + dp[j]

        dp[i] %= mod

        d[C[i]] = i

    print(dp[-1])


if __name__ == '__main__':
    main()

Solution (Python):






import sys
input = sys.stdin.readline

import math

import bisect
import heapq
from collections import defaultdict
from collections import deque
from collections import Counter
from functools import lru_cache





MOD = 10**9+7
INF = float('inf')
AZ = "abcdefghijklmnopqrstuvwxyz"






def I(): return int(input().strip())
def S(): return input().strip()
def IL(): return list(map(int,input().split()))
def SL(): return list(map(str,input().split()))
def ILs(n): return list(int(input()) for _ in range(n))
def SLs(n): return list(input().strip() for _ in range(n))
def ILL(n): return [list(map(int, input().split())) for _ in range(n)]
def SLL(n): return [list(map(str, input().split())) for _ in range(n)]


def P(arg): print(arg); return
def Y(): print("Yes"); return
def N(): print("No"); return
def E(): exit()
def PE(arg): print(arg); exit()
def YE(): print("Yes"); exit()
def NE(): print("No"); exit()


def DD(arg): return defaultdict(arg)


def inv(n): return pow(n, MOD-2, MOD)


kaijo_memo = []
def kaijo(n):
  if(len(kaijo_memo) > n): return kaijo_memo[n]
  if(len(kaijo_memo) == 0): kaijo_memo.append(1)
  while(len(kaijo_memo) <= n): kaijo_memo.append(kaijo_memo[-1] * len(kaijo_memo) % MOD)
  return kaijo_memo[n]

gyaku_kaijo_memo = []
def gyaku_kaijo(n):
  if(len(gyaku_kaijo_memo) > n): return gyaku_kaijo_memo[n]
  if(len(gyaku_kaijo_memo) == 0): gyaku_kaijo_memo.append(1)
  while(len(gyaku_kaijo_memo) <= n): gyaku_kaijo_memo.append(gyaku_kaijo_memo[-1] * pow(len(gyaku_kaijo_memo),MOD-2,MOD) % MOD)
  return gyaku_kaijo_memo[n]

def nCr(n,r):
  if n == r: return 1
  if n < r or r < 0: return 0
  ret = 1
  ret = ret * kaijo(n) % MOD
  ret = ret * gyaku_kaijo(r) % MOD
  ret = ret * gyaku_kaijo(n-r) % MOD
  return ret


def factorization(n):
  arr = []
  temp = n
  for i in range(2, int(-(-n**0.5//1))+1):
    if temp%i==0:
      cnt=0
      while temp%i==0: 
        cnt+=1 
        temp //= i
      arr.append([i, cnt])
  if temp!=1: arr.append([temp, 1])
  if arr==[]: arr.append([n, 1])
  return arr


def make_divisors(n):
  divisors = []
  for i in range(1, int(n**0.5)+1):
    if n % i == 0:
      divisors.append(i)
      if i != n // i: 
        divisors.append(n//i)
  return divisors


def make_primes(N):
  max = int(math.sqrt(N))
  seachList = [i for i in range(2,N+1)]
  primeNum = []
  while seachList[0] <= max:
    primeNum.append(seachList[0])
    tmp = seachList[0]
    seachList = [i for i in seachList if i % tmp != 0]
  primeNum.extend(seachList)
  return primeNum


def gcd(a, b):
    while b: a, b = b, a % b
    return a


def lcm(a, b):
    return a * b // gcd (a, b)


def count_bit(n):
  count = 0
  while n:
    n &= n-1
    count += 1
  return count


def base_10_to_n(X, n):
  if X//n: return base_10_to_n(X//n, n)+[X%n]
  return [X%n]

def base_n_to_10(X, n):
  return sum(int(str(X)[-i-1])*n**i for i in range(len(str(X))))

def base_10_to_n_without_0(X, n):
  X -= 1
  if X//n: return base_10_to_n_without_0(X//n, n)+[X%n]
  return [X%n]


def int_log(n, a):
  count = 0
  while n>=a:
    n //= a
    count += 1
  return count





N = I()
A = ILs(N)

dic = DD(list)
for i in range(N):
  dic[A[i]].append(i)
  
dp = [0 for i in range(N)]
dp[0] = 1
for i in range(N):
  c = A[i]
  p = bisect.bisect(dic[c],i)
  if p < len(dic[c]):
    if dic[c][p] != i+1:
      dp[dic[c][p]] += dp[i]
      dp[dic[c][p]]  %= MOD
  if i+1 < N:
    dp[i+1] += dp[i]
    dp[i+1] %= MOD

print(dp[-1])

Solution (Python):
N = int(input())
s = set()
dic = {}
memo = [0]*(N+1)
sm = {}
memo[0] = 1
P = 10**9 + 7
b = 0

for i in range(1,N+1):
  c = int(input())
  if c not in s:
    s.add(c)
    dic[c] = [i]
    memo[i] = memo[i-1]
  else:
    memo[i] = memo[i-1]
    if b != c:
      if len(dic[c]) == 1:
        sm[c] = memo[dic[c][0]-1]
      else:
        sm[c] += memo[dic[c][-1]-1]
      memo[i] += sm[c]
      memo[i] %= P
      dic[c].append(i)
  b = c
      
print(memo[N])

Solution (Python):
import sys


input_methods=['clipboard','file','key']
using_method=0
input_method=input_methods[using_method]

tin=lambda : map(int, input().split())
lin=lambda : list(tin())
mod=1000000007



def main():
	n = int(input())
	
	
	dd = dict()
	
	v = int(input())
	dd[v] = 0
	ll=[0]*n
	ll[0]=1
	for i in range(1, n):
		v = int(input())
		if v not in dd or dd[v] == i-1:
			ll[i] = ll[i-1]
			dd[v] = i
		else:
			ll[i] = (ll[i-1] + ll[dd[v]])%mod
			dd[v] = i
	return ll[-1]
			
		
	
	
	
	

isTest=False

def pa(v):
	if isTest:
		print(v)
		
def input_clipboard():
	import clipboard
	input_text=clipboard.get()
	input_l=input_text.splitlines()
	for l in input_l:
		yield l

if __name__ == "__main__":
	if sys.platform =='ios':
		if input_method==input_methods[0]:
			ic=input_clipboard()
			input = lambda : ic.__next__()
		elif input_method==input_methods[1]:
			sys.stdin=open('inputFile.txt')
		else:
			pass
		isTest=True
	else:
		pass
		
			
	ret = main()
	if ret is not None:
		print(ret)

Solution (Python):
import sys
input = lambda : sys.stdin.readline().rstrip()
sys.setrecursionlimit(max(1000, 10**9))
write = lambda x: sys.stdout.write(x+"\n")


n = int(input())
c = [None]*n
for i in range(n):
    c[i] = int(input())
    
dp = [0]*(n+1)
dp[0] = 1
M = 10**9+7

d = {}
for i,cc in enumerate(c):
    if cc not in d or d[cc]==i-1:
        dp[i+1] = dp[i]
    else:
        dp[i+1] = dp[i] + dp[d[cc]+1]
    d[cc] = i
    dp[i+1] %= M
print(dp[n])

Solution (Python):
n = int(input())
a = [int(input()) for _ in range(n)]
MOD = 10**9+7

na = [a[0]]
for i in range(n-1):
    if a[i] != a[i+1]:
        na.append(a[i+1])
        
m = len(na)
cur = [-1]*(max(na)+1)

dp = [0]*(m+1)
dp[0] = 1
for i in range(m):
    if cur[na[i]] != -1:
        dp[i+1] = (dp[i] + dp[cur[na[i]]]) % MOD
        cur[na[i]] = i+1
    else:
        cur[na[i]] = i+1
        dp[i+1] = dp[i]
        
print(dp[m])

Solution (Python):
N = int(input())
L = [-1] * (2 * 10 ** 5 + 1)
mod = 10 ** 9 + 7

dp = [0] * (N + 1)

dp[0] = 1

for i in range(N):
    dp[i+1] += dp[i]
    color = int(input())
    if L[color] != -1 and L[color] != i:
        dp[i+1] += dp[L[color]]
    L[color] = i+1
    dp[i+1] %= mod

print(dp[N])

Solution (Python):
def main():
    import sys
    read = sys.stdin.buffer.read
    readline = sys.stdin.buffer.readline
    readlines = sys.stdin.buffer.readlines
    sys.setrecursionlimit(10 ** 7)

    from collections import defaultdict

    n = int(readline())
    dp = [0] * (n + 1)
    dp[0] = 1
    memo = defaultdict(int)
    mod = 10 ** 9 + 7
    for i in range(1, n + 1):
        c = int(readline())
        dp[i] = dp[i - 1]
        if 0 < memo[c] < i - 1:
            dp[i] += dp[memo[c]]
        memo[c] = i
        dp[i] %= mod
    print(dp[n])


if __name__ == '__main__':
    main()

Solution (Python):
def resolve():
    n = int(input())
    c = [int(input()) for i in range(n)]
    lac = [-1]* 200010
    dp = [0]*n

    dp[0] = 1
    lac[c[0]] = 0
    for i in range(1, n):
        if c[i] == c[i-1]:
            dp[i] = dp[i-1]
        elif lac[c[i]] == -1:
            dp[i] = dp[i-1]
        else:
            dp[i] = dp[i-1] + dp[lac[c[i]]]
        lac[c[i]] = i
    print(dp[n-1]%(10**9+7))
resolve()

Solution (Python):
n = int(input())
iro = [-1 for i in range(2*(10**5)+1)]
dp = [1 for i in range(n+1)]
mod = 10**9 + 7
for i in range(1,n+1):
    dp[i] = dp[i-1]
    now = int(input())
    if iro[now] != -1 and iro[now] != i-1:
        dp[i] += dp[iro[now]]
    iro[now] = i
    dp[i] %= mod
print(dp[n])

Solution (Python):
n = int(input())
c = [int(input()) for _ in range(n)]
v_c = []
MOD = 10**9+7

for i,v in enumerate(c):
    if i > 0 and v == c[i-1]:
        continue
    v_c.append(v)

dp = [1]*(n+1)
color_cnt = [-1]*(2*10**5+5)
for i in range(1, len(v_c)+1):
    color = v_c[i-1]
    if color_cnt[color] > 0:
        dp[i] = dp[i-1] + dp[color_cnt[color]]
    else:
        dp[i] = dp[i-1]
    dp[i] %= MOD
    color_cnt[color] = i
print(dp[len(v_c)])

Solution (Python):
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

n = int(readline())
c = [0] + list(map(int,read().split()))

mod = 10**9 + 7
m = 2*10**5

before = [-1] * (m+1)
dp = [0] * (n+1)
dp[0] = 1

for i,ci in enumerate(c[1:],1):
    if(c[i-1]==ci):
        dp[i] = dp[i-1]
        continue

    if(before[ci] == -1):
        dp[i] = dp[i-1]
        before[ci] = i
        continue

    dp[i] = (dp[i-1] + dp[before[ci]])%mod
    before[ci] = i

print(dp[-1])

Solution (Python):
N = int(input())
MOD = 10**9 + 7
C = [int(input()) for i in range(N)]

dp = [0] * (N+1)
dp[0] = 1
last_idx = {}
for i, c in enumerate(C, 1):
  dp[i] = dp[i-1]
  if c in last_idx:
    idx = last_idx[c]
    if idx != i - 1:
      dp[i] += dp[idx]
      dp[i] %= MOD
  last_idx[c] = i

print(dp[-1]%MOD)

Solution (Python):
import sys
read = sys.stdin.buffer.read
input = sys.stdin.readline
input = sys.stdin.buffer.readline





def RD(): return sys.stdin.read()
def II(): return int(input())
def MI(): return map(int,input().split())
def MF(): return map(float,input().split())
def LI(): return list(map(int,input().split()))
def LF(): return list(map(float,input().split()))
def TI(): return tuple(map(int,input().split()))




def main():
	n=II()
	C=[]
	pre=0
	for i in range(n):
		a=II()
		if a!=pre:
			C.append(a)
		pre=a
	

	n=len(C)
	dp=[0]*(n+1)
	dp[1]=1
	li=[0]*(max(C)+10)
	li[C[0]]=1

	for i in range(1,n):
		
		
		dp[i+1]=(dp[i]+dp[li[C[i]]])%(10**9+7)
		li[C[i]]=i+1
	print(dp[-1])


if __name__ == "__main__":
	main()

Solution (Python):
n = int(input())
c = [-1] + [int(input()) for i in range(n)]

count = [0]*(200005)
dp = [0]*(n+1)
dp[0] = 1
mod = 10**9+7

for i in range(n):
    dp[i+1] = dp[i]
    if c[i+1] != c[i]:
        dp[i+1] += count[c[i+1]]
        dp[i+1] %= mod
        count[c[i+1]] += dp[i]
        count[c[i+1]] %= mod

print(dp[n]%mod)

Solution (Python):
mod = 10 ** 9 + 7
n = int(input())
c = [int(input()) for _ in range(n)]
import copy
cc = copy.deepcopy(c)
color_sum = {i: 0 for i in range(10 ** 6)}
dp = [1 for _ in range(n + 1)]
color_sum[cc[0]] = 1
for i in range(2, n + 1):
    dp[i] = dp[i - 1]
    if cc[i - 2] == cc[i - 1]:
        continue
    dp[i] += color_sum[cc[i - 1]]
    dp[i] %= mod
    color_sum[c[i - 1]] += dp[i - 1]
    color_sum[c[i - 1]] %= mod
print(dp[n])

Solution (Python):
n = int(input())
c = [int(input()) for _ in range(n)]
mod = 10 ** 9 + 7

color_sum = {i: 0 for i in range(10 ** 6)}
dp = [1 for _ in range(n+1)]
dp[0] = 1
dp[1] = 1
color_sum[c[0]] = 1

for i in range(2, n+1):
    dp[i] = dp[i-1]

    if c[i-2] == c[i-1]:
        continue

    dp[i] += color_sum[c[i-1]]
    dp[i] %= mod

    color_sum[c[i-1]] += dp[i-1]
    color_sum[c[i-1]] %= mod


print(dp[n])

Solution (Python):

import sys
sys.setrecursionlimit(10**9)
INF=10**18
MOD=10**9+7
input=lambda: sys.stdin.readline().rstrip()
YesNo=lambda b: bool([print('Yes')] if b else print('No'))
YESNO=lambda b: bool([print('YES')] if b else print('NO'))
int1=lambda x:int(x)-1

N=int(input())
C=[]
MAX=-1
for i in range(N):
    c=int1(input())
    MAX=max(MAX,c)
    if not C or (C and C[-1]!=c):
        C.append(c)
M=len(C)
dp=[0]*(M+1)
dp[0]=1
last=[-1]*(MAX+1)
for i in range(M):
    if last[C[i]]!=-1:
        dp[i+1]+=dp[i]+dp[last[C[i]]]
    else:
        dp[i+1]=dp[i]
    dp[i+1]%=MOD
    last[C[i]]=i+1
print(dp[-1])

Solution (Python):
N = int(input())
C = [int(input()) for _ in range(N)]
MOD = 10**9 + 7

if N <= 2:
    print(1)
    exit()

dp = [1,1]
last_idx = [-1]*(2*10**5 + 1)
last_idx[C[0]] = 0
last_idx[C[1]] = 1

for i in range(2, N):
    if C[i-1] == C[i] or last_idx[C[i]] == -1:
        dp.append(dp[-1] % MOD)
    else:
        dp.append((dp[-1] + dp[last_idx[C[i]]]) % MOD)
    last_idx[C[i]] = i

print(dp[-1])

Solution (Python):
N = int(input())
C = [int(input()) for _ in range(N)]
MOD = 10**9 + 7

if N <= 2:
    print(1)
    exit()

dp = [1,1]
last_idx = [-1]*(N+10)
last_idx[C[0]] = 0
last_idx[C[1]] = 1

for i in range(2, N):
    if C[i-1] == C[i] or last_idx[C[i]] == -1:
        dp.append(dp[-1] % MOD)
    else:
        dp.append((dp[-1] + dp[last_idx[C[i]]]) % MOD)
    last_idx[C[i]] = i

print(dp[-1])

Solution (Python):
N = int(input())
C = [int(input()) for _ in range(N)]
MOD = 10**9 + 7

if N <= 2:
    print(1)
    exit()

dp = [1,1]
last_idx = [-1]*(N+10)
last_idx[C[0]] = 0
last_idx[C[1]] = 1

for i in range(2, N):
    if C[i-1] == C[i] or last_idx[C[i]] == -1:
        dp.append(dp[-1] % MOD)
    else:
        dp.append((dp[-1] + dp[last_idx[C[i]]]) % MOD)
    last_idx[C[i]] = i

print(dp[-1])

Solution (Python):
import sys

sys.setrecursionlimit(10 ** 6)
INF = float("inf")
MOD = 10 ** 9 + 7


def input():
    return sys.stdin.readline().strip()


def main():
    N = int(input())
    C = [int(input()) for _ in range(N)] + [-1]
    C = [C[i] for i in range(N) if C[i] != C[i + 1]]

    N = len(C)
    
    dp = [0] * N
    dp[0] = 1
    used = [-1] * (max(C) + 1)
    used[C[0]] = 0

    for i in range(1, N):
        if used[C[i]] == -1:
            dp[i] = dp[i - 1]
        else:
            dp[i] = dp[i - 1] + dp[used[C[i]]]

        dp[i] %= MOD
        used[C[i]] = i

    print(dp[-1])


if __name__ == "__main__":
    main()

Solution (Python):
import sys
def input(): return sys.stdin.readline().rstrip()
def main():
    n=int(input())
    mod=10**9+7
    stone_last_pos=[-1]*(2*10**5+1)
    dp=[0]*(n+1)
    dp[0]=1
    for i in range(1,n+1):
        c=int(input())
        place=stone_last_pos[c]
        if place==i-1 or place==-1:
            dp[i]=dp[i-1]
        else:
            dp[i]=(dp[i-1]+dp[place])%mod
        stone_last_pos[c]=i
    print(dp[n])


if __name__=='__main__':
    main()

Solution (Python):
import sys
def input(): return sys.stdin.readline().rstrip()
def main():
    n=int(input())
    mod=10**9+7
    stone_last_pos=[-1]*(2*10**5+1)
    dp=[0]*(n+1)
    dp[0]=1
    for i in range(1,n+1):
        c=int(input())
        place=stone_last_pos[c]
        if place==i-1 or place==-1:
            dp[i]=dp[i-1]
        else:
            dp[i]=(dp[i-1]+dp[place])%mod
        stone_last_pos[c]=i
    print(dp[n])


if __name__=='__main__':
    main()

Solution (Python):
import sys
def input(): return sys.stdin.readline().rstrip()
def main():
    n=int(input())
    mod=10**9+7
    stone=[0]*(2*10**5+1)
    stone_last_pos=[-1]*(2*10**5+1)
    dp=[0]*(n+1)
    dp[0]=1
    for i in range(1,n+1):
        c=int(input())
        place=stone_last_pos[c]
        if place==i-1 or place==-1:
            dp[i]=dp[i-1]
        else:
            dp[i]=(dp[i-1]+dp[place])%mod
        stone_last_pos[c]=i
    print(dp[n])


if __name__=='__main__':
    main()

Solution (Python):
import sys,queue,math,copy,itertools,bisect,collections,heapq

def main():
    sys.setrecursionlimit(10**7)
    INF = 10**18
    MOD = 10**9 + 7
    LI = lambda : [int(x) for x in sys.stdin.readline().split()]
    NI = lambda : int(sys.stdin.readline())
    SI = lambda : sys.stdin.readline().rstrip()

    N = NI()
    CMAX = 2*10**5
    A = [0 for _ in range(CMAX+1)]
    S = [1 for _ in range(CMAX+1)]
    C = [NI() for _ in range(N)]
    P = 1
    A[C[0]] = 1
    for i in range(1,N):
        if C[i] != C[i-1] and A[C[i]] > 0:
            S[C[i]] = S[C[i]] + P
        else:
            S[C[i]] = P
        A[C[i]] = 1
        P = S[C[i]] % MOD
    print(P)


if __name__ == '__main__':
    main()

Solution (Python):
n=int(input())
c=[int(input()) for _ in range(n)]
color_sum=[0]*200001
dp=[0]*(n+1)
dp[0]=1
dp[1]=1
color_sum[c[0]]+=1


for i in range(1,n): 
  dp[i+1]=dp[i]
  if c[i]==c[i-1]:
    continue
  dp[i+1]+=color_sum[c[i]]
  color_sum[c[i]]=dp[i+1]
print(dp[n]%(pow(10,9)+7))

Solution (Python):
MOD = 10**9 + 7
N = int(input())
C = [int(input()) for _ in range(N)]
dp = [0]*(N+1)
lis = [-1] * (2 * 10**5 + 1)
dp[0] = 1
lis[C[0]] = 0
for i,c in enumerate(C[1:],1):
    prev_i = lis[c]
    dp[i] = dp[i-1]
    if prev_i != i-1:
        dp[i] += dp[prev_i]
        dp[i] %= MOD
    lis[c] = i
answer = dp[N-1]
print(answer)

Solution (Python):
N = int(input())
C = [int(input()) for _ in range(N)]

mod = 10**9+7
newC = [C[0]]
for c in C:
    if newC[-1] == c:
        continue
    newC.append(c)

N = len(newC)
L = [0]*(N+1)
L[0] = 1
idx = [-1]*(max(newC)+1)
for i in range(N):
    if idx[newC[i]] >= 0:
        L[i+1] += L[idx[newC[i]]]
        
    L[i+1] += L[i]
    L[i+1] %= mod
    idx[newC[i]] = i+1

print(L[-1])

Solution (Python):
n = int(input())

cl = []

for i in range(n):
    cl.append(int(input()))


ans = [1 for i in range(n)]

mod = 10**9+7

stones = dict()

stones[cl[-1]] = n-1

for i in range(n-1):
    cur = cl[n-i-2]

    if cur in stones and stones[cur] != n-i-1:
        ans[n-i-2] = ans[n-i-1] + ans[stones[cur]]
        ans[n-i-2] %= mod
    else:
        ans[n-i-2] = ans[n-i-1] % mod
    stones[cur] = n-i-2

print(ans[0])

Solution (Python):
n = int(input())
c = [int(input()) for _i in range(n)]
c.append(-1)
dic = [-1 for _i in range(10**5 *2 +1)]
dp = [0 for _i in range(n+1)]
dp[n] = 1
mod = 10**9 +7
for i in range(n):
    if c[i-1] != c[i]:
        if dic[c[i]] > 0:
            dp[i] = (dp[i-1] + dic[c[i]])%mod
        else:
            dp[i] = dp[i-1]
        dic[c[i]] = dp[i]
    else:
        dp[i] = dp[i-1]
    
print(dp[n-1]%mod)

Solution (Python):
n = int(input())
c = [int(input()) for _i in range(n)]
c.append(-1)
dic = [-1 for _i in range(10**5 *2 +1)]
dp = [0 for _i in range(n+1)]
dp[n] = 1
mod = 10**9 +7
for i in range(n):
    if c[i-1] != c[i]:
        if dic[c[i]] > 0:
            dp[i] = (dp[i-1] + dic[c[i]])%mod
        else:
            dp[i] = dp[i-1]
        dic[c[i]] = dp[i]
    else:
        dp[i] = dp[i-1]
    
print(dp[n-1]%mod)

Solution (Python):
n = int(input())
c = [int(input()) for _i in range(n)]
c.append(-1)
dic = {}
dp = [0 for _i in range(n+1)]
dp[n] = 1
mod = 10**9 +7
for i in range(n):
    if c[i-1] != c[i]:
        if c[i] in dic:
            dp[i] = (dp[i-1] + dic[c[i]])%mod
        else:
            dp[i] = dp[i-1]
        dic[c[i]] = dp[i]
    else:
        dp[i] = dp[i-1]
    
print(dp[n-1]%mod)

Solution (Python):
n = int(input())
c = [int(input()) for _i in range(n)]
c.append(-1)
dic = {}
dp = [0 for _i in range(n+1)]
dp[n] = 1
mod = 10**9 +7
for i in range(n):
    if c[i-1] != c[i]:
        if c[i] in dic:
            dp[i] = (dp[i-1] + dic[c[i]])%mod
        else:
            dp[i] = dp[i-1]
        dic[c[i]] = dp[i]
    else:
        dp[i] = dp[i-1]
    
print(dp[n-1]%mod)

Solution (Python):
import numpy as np
from collections import defaultdict
from operator import itemgetter
import sys

input = sys.stdin.readline

MOD = 10 ** 9 + 7


d = defaultdict(list)

N = int(input())
for i in range(N):
    C = int(input())
    d[C].append(i)

pairs = []
for c, indices in d.items():
    for i in range(len(indices) - 1):
        if indices[i+1] - indices[i] > 1:
            pairs.append((indices[i], indices[i+1]))

pairs.sort(key = itemgetter(1))   


dp = np.zeros(N, np.int64)
dp[0] = 1
index = 0
for i in range(1, N):
    dp[i] = dp[i-1]
    while index < len(pairs) and pairs[index][1] == i:
        dp[i] += dp[pairs[index][0]] 
        index += 1
    dp[i] %= MOD

print(dp[-1])

Solution (Python):
import sys

sys.setrecursionlimit(10 ** 5)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def SI(): return sys.stdin.readline()[:-1]

def main():
    n=II()
    aa=[]
    cnt=[0]*200005
    for _ in range(n):
        c=II()
        if not aa or aa[-1]!=c:aa.append(c)
    
    md=10**9+7
    ans=1
    for a in aa:
        cnt[a]=(cnt[a]+ans)%md
        ans=cnt[a]
    print(ans)

main()

Solution (Python):
from collections import defaultdict
from bisect import *
def solve():
    mod = 10**9+7
    d = defaultdict(lambda: [])
    N = int(input())
    for i in range(N):
        a = int(input())
        d[a].append(i)
    selist = [[-1,-1]]
    ends = [-1]
    for l in d.values():
        for i in range(len(l)-1):
            if l[i+1]-1>l[i]:
                selist.append([l[i],l[i+1]])
                ends.append(l[i+1])
    selist = sorted(selist,key=lambda x:x[1])
    ends.sort()
    dp = [0]*(len(selist))
    for i in range(1,len(selist)):
        dp[i] = dp[i-1]+1
        ind = bisect_right(ends,selist[i][0])
        dp[i] += dp[ind-1]
        dp[i] %= mod
    ans = dp[-1]+1
    ans %= mod
    return ans
print(solve())

Solution (Python):
from collections import defaultdict
from bisect import *
def solve():
    mod = 10**9+7
    d = defaultdict(lambda: [])
    N = int(input())
    for i in range(N):
        a = int(input())
        d[a].append(i)
    selist = []
    ends = [-1]
    for l in d.values():
        for i in range(len(l)-1):
            if l[i+1]-1>l[i]:
                selist.append([l[i],l[i+1]])
                ends.append(l[i+1])
    selist = [[-1,-1]]+sorted(selist,key=lambda x:x[1])
    
    
        
    
    ends.sort()
    dp = [0]*(len(selist))
    for i in range(1,len(selist)):
        dp[i] = dp[i-1]+1
        ind = bisect_right(ends,selist[i][0])
        dp[i] += dp[ind-1]
        dp[i] %= mod
    ans = dp[-1]+1
    ans %= mod
    return ans
print(solve())

Solution (Python):
from collections import defaultdict
from bisect import *
def solve():
    mod = 10**9+7
    d = defaultdict(lambda: [])
    N = int(input())
    for i in range(N):
        a = int(input())
        d[a].append(i)
    selist = []
    ends = [-1]
    for l in d.values():
        for i in range(len(l)-1):
            if l[i+1]-1>l[i]:
                selist.append([l[i],l[i+1]])
                ends.append(l[i+1])
    selist = [[-1,-1]]+sorted(selist,key=lambda x:x[1])
    
    
        
    
    ends.sort()
    dp = [0]*(len(selist))
    for i in range(1,len(selist)):
        dp[i] = (dp[i-1]+1)%mod
        ind = bisect_right(ends,selist[i][0])
        dp[i] += dp[ind-1]
    ans = dp[-1]+1
    ans %= mod
    return ans
print(solve())

Solution (Python):
from collections import defaultdict
from bisect import *
def solve():
    mod = 10**9+7
    d = defaultdict(lambda: [])
    N = int(input())
    for i in range(N):
        a = int(input())
        d[a].append(i)
    selist = []
    ends = [-1]
    for l in d.values():
        for i in range(len(l)-1):
            if l[i+1]-1>l[i]:
                selist.append([l[i],l[i+1]])
                ends.append(l[i+1])
    selist = [[-1,-1]]+sorted(selist,key=lambda x:x[1])
    
    
        
    
    ends.sort()
    dp = [0]*(len(selist))
    for i in range(1,len(selist)):
        dp[i] = dp[i-1]+1
        ind = bisect_right(ends,selist[i][0])
        dp[i] += dp[ind-1]
    ans = dp[-1]+1
    ans %= mod
    return ans
print(solve())

Solution (Python):
n = int(input())
c = [int(input()) for _ in range(n)]
mod = 10 ** 9 + 7
MAX = 2 * 10 ** 5

cc = []
prev = 0
for e in c:
    if e != prev:
        cc.append(e)
        prev = e

ln = len(cc)

dp_prev = 1
acc = [0] * (MAX + 1)

for i, e in enumerate(cc, 1):
    dp_now = dp_prev + acc[e]
    dp_now %= mod

    acc[e] += dp_prev
    acc[e] %= mod

    dp_prev = dp_now

print(dp_now)

Solution (Python):
n = int(input())
c = [int(input()) for _ in range(n)]
mod = 10 ** 9 + 7
MAX = 2 * 10 ** 5

cc = []
prev = 0
for e in c:
    if e != prev:
        cc.append(e)
        prev = e

ln = len(cc)

dp = [0] * (ln + 1)
dp[0] = 1
acc = [0] * (MAX + 1)

for i, e in enumerate(cc, 1):
    dp[i] = dp[i-1] + acc[e]
    dp[i] %= mod

    acc[e] += dp[i-1]
    acc[e] %= mod

print(dp[ln])

Solution (Python):
import sys
read = sys.stdin.read
MOD = 10**9+7

n, *C = map(int, read().split())
dp = [0]*(n+1)
dp[0] = 1
idx = [-1]*(2*10**5+1)
for i, c in enumerate(C, 1):
  dp[i] = dp[i-1]
  if idx[c] != -1 and idx[c] < i-1:
    dp[i] += dp[idx[c]]
    dp[i] %= MOD
  idx[c] = i
print(dp[-1])

Solution (Python):
from collections import defaultdict
MOD = 10**9+7
n = int(input())
dp = [1]
d = defaultdict(list)
cur = int(input())
d[cur].append(0)
for i in range(1,n):
  pre,cur = cur,int(input())
  c = dp[-1]
  if pre != cur and d[cur]:
    c += dp[d[cur][-1]]
  dp.append(c%MOD)
  d[cur].append(i)
print(dp[-1])

Solution (Python):
from collections import defaultdict
MOD = 10**9+7
n = int(input())
dp = [1]
d = defaultdict(list)
cur = int(input())
d[cur].append(0)
for i in range(1,n):
  pre,cur = cur,int(input())
  c = dp[-1]
  if pre != cur and d[cur]:
    c += dp[d[cur][-1]]
  dp.append(c)
  d[cur].append(i)
print(dp[-1]%MOD)

Solution (Python):
from collections import Counter
MOD = pow(10,9)+7
N = int(input())
C = [int(input()) for i in range(N)]

DP = [1]*N
counter = Counter()
for i in range(N):
    c = C[i]
    if i==0:
        counter[c]+=1
    elif i==1:
        if c!=C[i-1]:
            counter[c]+=1
    else:
        DP[i] = DP[i-1]
        if c!=C[i-1]:
            DP[i]+=counter[c]
            counter[c]+=DP[i-1]
print(DP[N-1]%MOD)

Solution (Python):
n = int(input())
c = [int(input()) for _ in range(n)]
MOD = 10 ** 9 + 7

dp = [0] * (n + 1)
dp[0] = 1
prev = [-1] * (10 ** 6)
for i, x in enumerate(c):
    dp[i + 1] = dp[i]
    if 0 <= prev[x] < i:
        dp[i + 1] += dp[prev[x]]
        dp[i + 1] %= MOD
    prev[x] = i + 1
print(dp[n])

Solution (Python):
import sys
def input():
    return sys.stdin.readline()[:-1]
N=int(input())
pr=10**9+7
a=0
l=[0]*(2*10**5)
C=[int(input())-1 for i in range(N)]
for i in range(N-1):
    if C[i]==C[i+1]:
        continue
    a,l[C[i]]=(l[C[i]]+a)%pr,(l[C[i]]+a+1)%pr
a+=l[C[-1]]
print((a+1)%pr)

Solution (Python):



def main():
  MAX = 10**9 + 7
  
  n = int(input())
  lc = [int(input()) for _ in range(n)]
  dp = [0] * (n)
  
  last_is = [-1]*(2*10**5+1)
  dp[0] = 1
  last_is[lc[0]] = 0
  for i,c in enumerate(lc[1:], 1):
    last_i = last_is[c]
    dp[i] = dp[i-1]
    if last_i != -1 and last_i != i-1:
      dp[i] += dp[last_i]
      dp[i] %= MAX
    last_is[c] = i

  print(dp[-1])
  

if __name__=='__main__':
  main()

Solution (Python):
N=int(input())
A=[int(input()) for _ in range(N)]
mod=10**9+7
B=[A[0]-1]
for i in range(1,N):
  if A[i]!=A[i-1]:
    B.append(A[i]-1)
n=len(B)
used=[-1]*(max(A)+1)
used[B[0]]=0
dp=[0]*n
dp[0]=1
for i in range(1,n):
  if used[B[i]]==-1:
    dp[i]=dp[i-1]
  else:
    a=used[B[i]]
    dp[i]=(dp[i-1]+dp[a])%mod
  used[B[i]]=i
print(dp[-1])

Solution (Python):












N = int(input())
C = [None] * N
for i in range(N):
  C[i] = int(input())

DIV = 10 ** 9 + 7

dp = [0 for i in range(N)]
dp[0] = 1
index = [-1] * (max(C)+1) 
index[C[0]] = 0 

for i in range(1,len(C)):
  if C[i] == C[i-1]:
    dp[i] = dp[i-1] 
  elif index[C[i]] == -1:
    
    dp[i] = dp[i-1]
  else:
    
    dp[i] = ( dp[i-1] + dp[index[C[i]]] ) % DIV
  
  index[C[i]] = i

print(dp[-1])

Solution (Python):
MOD = 10 ** 9 + 7
n = int(input())
c = [int(input()) for _ in range(n)]
l = [c[0]]
for i in range(1, n):
    if c[i] != c[i - 1]:
        l.append(c[i])
n = len(l)
p = [-1] * (max(c) + 1)
q = [-1] * n
for i, x in enumerate(l[::-1]):
    q[n - i - 1] = p[x]
    p[x] = n - i - 1
dp = [0] * (n + 1)
dp[0] = 1
for i in range(n):
    dp[i + 1] += dp[i]
    if q[i] != -1:
        dp[q[i] + 1] += dp[i + 1]
print(dp[n] % MOD)

Solution (Python):
INF = 10 ** 9
MOD = 10 ** 9 + 7
import sys
sys.setrecursionlimit(100000000)
dy = (-1,0,1,0)
dx = (0,1,0,-1)
from  copy import deepcopy
from bisect import bisect_left

def main():
    n = int(input())
    C = [int(input()) for _ in range(n)]

    dic = {i:0 for i in set(C)}
    dp = [0] * (n + 1)
    dp[0] = 1
    for i in range(n):
        if i > 0 and C[i] == C[i - 1]:
            dp[i + 1] = dp[i]
            continue
        else:
            dp[i + 1] = (dp[i] + dic[C[i]])%MOD
            dic[C[i]] += dp[i]
            dic[C[i]] %= MOD
    print(dp[-1]%MOD)
    
if __name__ == '__main__':
    main()

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import accumulate, permutations, combinations, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
C = [INT() for _ in range(N)]
dp = [0]*(N+1)
dp[0] = 1
dp2 = [-1]*(max(C)+1)  
for i in range(1, N+1):
	p = dp2[C[i-1]]  
	if i-p > 1 and p != -1:  
		dp[i] += dp[p]
	dp2[C[i-1]] = i
	dp[i] += dp[i-1]
	dp[i] %= mod

print(dp[N])

Solution (Python):
N=int(input())
dp=[1 for i in range(0,N)]
data={i:-1 for i in range(1,2*10**5+1)}
mod=10**9+7

c=int(input())
data[c]=0

for i in range(1,N):
    c=int(input())
    if data[c]==i-1:
        dp[i]=dp[i-1]
    elif data[c]==-1:
        dp[i]=dp[i-1]
    else:
        dp[i]=(dp[i-1]+dp[data[c]])%mod
    data[c]=i

print(dp[N-1])