Problem:


Score : 400 points

Problem Statement

We have a board with a 2 \times N grid.
Snuke covered the board with N dominoes without overlaps.
Here, a domino can cover a 1 \times 2 or 2 \times 1 square.

Then, Snuke decided to paint these dominoes using three colors: red, cyan and green.
Two dominoes that are adjacent by side should be painted by different colors.
Here, it is not always necessary to use all three colors.

Find the number of such ways to paint the dominoes, modulo 1000000007.

The arrangement of the dominoes is given to you as two strings S_1 and S_2 in the following manner:

Each domino is represented by a different English letter (lowercase or uppercase).

The j-th character in S_i represents the domino that occupies the square at the i-th row from the top and j-th column from the left.

Constraints

1 \leq N \leq 52

|S_1| = |S_2| = N

S_1 and S_2 consist of lowercase and uppercase English letters.

S_1 and S_2 represent a valid arrangement of dominoes.

Input

Input is given from Standard Input in the following format:

N
S_1
S_2

Output

Print the number of such ways to paint the dominoes, modulo 1000000007.

Sample Input 1

3
aab
ccb

Sample Output 1

6

There are six ways as shown below:

Sample Input 2

1
Z
Z

Sample Output 2

3

Note that it is not always necessary to use all the colors.

Sample Input 3

52
RvvttdWIyyPPQFFZZssffEEkkaSSDKqcibbeYrhAljCCGGJppHHn
RLLwwdWIxxNNQUUXXVVMMooBBaggDKqcimmeYrhAljOOTTJuuzzn

Sample Output 3

958681902



Sample input:
3
aab
ccb


Sample output:
6

Submission status: Accepted

Solution code:
def main(sample_file = ''):

    """ convenient functions
    # for i, a in enumerate(iterable)
    # q, mod = divmod(a, b)
    # divmod(x, y) returns the tuple (x//y, x%y)
    # Higher-order function: reduce(operator.mul, xyz_count, 1)
    # manage median(s) using two heapq https://atcoder.jp/contests/abc127/tasks/abc127_f
    """

    """convenient decorator
    # @functools.lru_cache():
    # to facilitate use of recursive function
        # ex:
        # from functools import lru_cache
        # import sys
        # sys.setrecursionlimit(10**9)
        # @lru_cache(maxsize=None)
        # def fib(n):
        #     if n < 2:
        #         return n
        #     return fib(n-1) + fib(n-2)
        # print(fib(1000))
    """
    
    # import numpy as np
    import sys
    sys.setrecursionlimit(10**7)
    from itertools import accumulate, combinations, permutations, product # https://docs.python.org/ja/3/library/itertools.html
    # accumulate() returns iterator! to get list: list(accumulate())
    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 = []  # prime factor
        b, e = 2, 0  # base, exponent
        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
        """
        # TODO: How should I do when n - r is negative?
        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 # https://docs.python.org/ja/3/library/collections.html#collections.deque
    from heapq import heapify, heappop, heappush, heappushpop, heapreplace,nlargest,nsmallest # https://docs.python.org/ja/3/library/heapq.html
    from copy import deepcopy, copy # https://docs.python.org/ja/3/library/copy.html
    import operator
    from operator import itemgetter #sort 
    # ex1: List.sort(key=itemgetter(1))
    # ex2: sorted(tuples, key=itemgetter(1,2))
    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 # Deprecated since version 3.5: Use math.gcd() instead.
    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)
    
    # first create factorial_list
    # fac_list = mod_factorial_list(n)
    INF = 10 ** 18
    MOD = 10 ** 9 + 7
    AtoZ = list('abcdefghijklmnopqrsruvwxyz')
    modpow = lambda a, n, p = MOD: pow(a, n, p) # Recursive function in python is slow!
    def modinv(a, p = MOD):
        # evaluate reciprocal using Fermat's little theorem:
        # a**(p-1) is identical to 1 (mod p) when a and p is coprime
        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):
        # fac_list = modfactorial_list(100)
        # print(modcomb(100, 5, modfactorial_list(100)))
        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]

    # ************ Graph ************
    # Graph: https://en.wikipedia.org/wiki/Directed_graph
    # 最短経路問題: https://ja.wikipedia.org/wiki/%E6%9C%80%E7%9F%AD%E7%B5%8C%E8%B7%AF%E5%95%8F%E9%A1%8C
    
    # Bellman-Ford: O(|V||E|). Use this if there exists an edge with negative length in the graph
    # After N steps, the shortest path has converded if there doesn't exist an cycle of edges with negative
    # Watch out: d[N] == d[2*N] doesn't necessarily mean the graph doesn't have negative cycle
    # ref: https://www.youtube.com/watch?v=1Z6ofKN03_Y

    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]

    # Warshall Floyd O(V**3)
    def warshall_floyd(number_vertex, XYD, shift_one_for_vertex=False):
        # ref: https://juppy.hatenablog.com/entry/2018/11/01/%E8%9F%BB%E6%9C%AC_python_%E5%85%A8%E7%82%B9%E5%AF%BE%E6%9C%80%E7%9F%AD%E7%B5%8C%E8%B7%AF%E6%B3%95%EF%BC%88%E3%83%AF%E3%83%BC%E3%82%B7%E3%83%A3%E3%83%AB%E3%83%95%E3%83%AD%E3%82%A4%E3%83%89%E6%B3%95
        # number_vertex: len(vertex)
        # XYD: list of distance from x to y
        # shift_one_for_vertex: XYDの値が1~Nの時(0~N-1でない時)に調整するフラグ。
        # d[i][j]: iからjへの最短距離
        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 # distance of same vertex is 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
    # initialize variables
        # to initialize list, use [0] * n
        # to initialize two dimentional array:
            # ex) [[0] * N for _ in range(N)]
            # ex2) dp = [[0] * (N+1) for _ in range(W*2)]
    # set inputs
        # put inputs between specific values (almost as quickly)
        # ex) S = [-INF] + [int(r()) for _ in range(A)] + [INF]
        # open(0).read() is sometimes useful:
        # ex) n, m, *x = map(int, open(0).read().split())
        #     min(x[::2]) - max(x[1::2])
        # ex2) *x, = map(int, open(0).read().split())
        #     don't forget to add comma after *x if only one variable is used
    # preprocessing
        # transpose = [x for x in zip(*data)]
        # ex) [[1, 2, 3], [4, 5, 6], [7, 8, 9]] => [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
        # flat = [flatten for inner in data for flatten in inner]
        # ex) [[1, 2, 3], [4, 5, 6], [7, 8, 9]] => [1, 2, 3, 4, 5, 6, 7, 8, 9]
    # calculate and output
        # output pattern
        # ex1) print(*l) => when l = [2, 5, 6], printed 2 5 6
    """

    # functions to read input
    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
    # single int: int(r())
    # single string: r()
    # single float: float(r())
    # line int: R()
    # line string: r().split()
    # line (str, int, int): [j if i == 0 else int(j) for i, j in enumerate(r().split())]
    # lines int: [R() for _ in range(n)]
    """

    # for test
    if sample_file:
        sys.stdin = open(sample_file)
        
    # ----------------------------------
    # main
    #%%
    N = r_int()
    S1 = r()
    S2 = r()
    i = 0
    ans = 0
    # N == 1のパターン
    if N == 1:
        print(3)
        return
    # N == 2のパターン
    if N == 2:
        if S1[0] == S1[1]:
            print(6)
            return
        else:
            print(6) # 結局6
            return
    # N == 3
    if N == 3:
        if S1[0] != S1[1] and S1[1] != S1[2]:
            print(12)
            return
        else:
            print(6)
            return
    # N >= 4
    if S1[0] == S1[1]:
        ans = 6
        i = 2
        reset_flag = 0
    else:
        ans = 3
        i = 1
        reset_flag = 1
    while True: # インデックスを無限ループで増やしていく
        if reset_flag == 0:
            if S1[i] == S1[i+1]:
                ans = (ans*3)%1000000007
                i += 2
                reset_flag = 0
            else:
                ans = ans
                i += 1
                reset_flag = 1
        else:
            if S1[i] == S1[i+1]:
                ans = (ans*2)%1000000007
                i += 2
                reset_flag = 0
            else:
                ans = (ans*2)%1000000007
                i += 1
                reset_flag = 1
        # 終了条件を記述する
        if i == N:
            print(ans)
            return
        elif i == N-1:
            if reset_flag == 0:
                print(ans)
                return
            else:
                print((ans*2)%1000000007)
                return

    #%%
    # end of main
    # ----------------------------------

    """memo: how to use defaultdict of list
    # initialize
    Dic = defaultdict(list)
    # append / extend
    Dic[x].append(y)
    # three methods for loop: keys(), values(), items()
    for k, v in Dic.items():
    """
    
    """memo: how to solve binary problems
    # to make binary digits text
    >>> a = 5
    >>> bin_str_a = format(a, '#06b')
    >>> print(bin_str_a)
    0b0101 # first 2 strings (='0b') indicates it is binary
    """
    
    """memo: how to solve the problem
    creating simple test/answer
    greed
    simple dp
    graph
    """

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline

P = 10 ** 9 + 7


def main():
    N = int(input())
    S1 = input().rstrip()
    S2 = input().rstrip()

    if S1[0] == S2[0]:
        ans = 3
        i = 1
        prev = "H"
    else:
        ans = 6
        i = 2
        prev = "W"

    while i < N:
        if S1[i] == S2[i]:
            if prev == "H":
                ans *= 2
            else:
                ans *= 1
            i += 1
            prev = "H"
        else:
            if prev == "H":
                ans *= 2
            else:
                ans *= 3
            i += 2
            prev = "W"
    print(ans % P)


if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
n=int(input())
a=input()
b=input()
if a[0]!=b[0]:
  x=6
  p=2
  f=1
else:
  x=3
  p=1
  f=0
while p<n:
  if f:
    if a[p]!=b[p]:
      p+=2
      x*=3
    else:
      p+=1
      f=0
  else:
    if a[p]!=b[p]:
      p+=2
      x*=2
      f=1
    else:
      p+=1
      x*=2
print(x%(10**9+7))

Submission status: Accepted

Solution code:
from sys import stdin
def main():
    #入力
    readline=stdin.readline
    mod=10**9+7
    N=int(readline())
    S1=readline().strip()
    S2=readline().strip()

    now=0
    before="Z"
    res=1
    while now<N:
        if S1[now]==S2[now]:
            if now==0:
                res*=3
            else:
                if before=="X":
                    res*=2
                else:
                    res*=1
            now+=1
            before="X"
        else:
            if now==0:
                res*=6
            else:
                if before=="X":
                    res*=2
                else:
                    res*=3
            now+=2
            before="Y"

    print(res%mod)
if __name__=="__main__":
    main()

Submission status: Accepted

Solution code:
N = int(input())
mod = 10 ** 9 + 7
S1 = input()
S2 = input()

i = 0
d = []
while i < N:
    if S1[i] == S2[i]:
        d.append(1)
        i += 1
    else:
        d.append(2)
        i += 2

memo = 3 if d[0] == 1 else 6
for x, y in zip(d[:-1], d[1:]):
    if (x, y) == (1, 1):
        memo *= 2
    elif (x, y) == (1, 2):
        memo *= 2
    elif (x, y) == (2, 1):
        memo *= 1
    else:
        memo *= 3
    memo %= mod

print(memo)

Submission status: Accepted

Solution code:
n=int(input())
s=input()
t=input()
n=len(s)
mod=10**9+7
ans=1
i=0
while i<n:
  if i==0:
    if s[i]==t[i]: 
      ans*=3
      i+=1
    else:
      ans*=6
      i+=2
    continue
  if s[i-1]!=t[i-1] and s[i]==t[i]:
    ans*=1
    i+=1
  elif s[i-1]==t[i-1] and s[i]!=t[i]:
    ans*=2
    i+=2
  elif s[i-1]!=t[i-1] and s[i]!=t[i]:
    ans*=3
    i+=2
  elif s[i-1]==t[i-1] and s[i]==t[i]:
    ans*=2
    i+=1
  ans%=mod
print(ans)

Submission status: Accepted

Solution code:
N=int(input())
S1=input()
S2=input()

MOD = 10**9+7
class Mint:
    def __init__(self, value=0):
        self.value = value % MOD
        if self.value < 0: self.value += MOD

    @staticmethod
    def get_value(x): return x.value if isinstance(x, Mint) else x

    def inverse(self):
        a, b = self.value, MOD
        u, v = 1, 0
        while b:
            t = a // b
            b, a = a - t * b, b
            v, u = u - t * v, v
        if u < 0: u += MOD
        return u

    def __repr__(self): return str(self.value)
    def __eq__(self, other): return self.value == other.value
    def __neg__(self): return Mint(-self.value)
    def __hash__(self): return hash(self.value)
    def __bool__(self): return self.value != 0

    def __iadd__(self, other):
        self.value = (self.value + Mint.get_value(other)) % MOD
        return self
    def __add__(self, other):
        new_obj = Mint(self.value)
        new_obj += other
        return new_obj
    __radd__ = __add__

    def __isub__(self, other):
        self.value = (self.value - Mint.get_value(other)) % MOD
        if self.value < 0: self.value += MOD
        return self
    def __sub__(self, other):
        new_obj = Mint(self.value)
        new_obj -= other
        return new_obj
    def __rsub__(self, other):
        new_obj = Mint(Mint.get_value(other))
        new_obj -= self
        return new_obj

    def __imul__(self, other):
        self.value = self.value * Mint.get_value(other) % MOD
        return self
    def __mul__(self, other):
        new_obj = Mint(self.value)
        new_obj *= other
        return new_obj
    __rmul__ = __mul__

    def __ifloordiv__(self, other):
        other = other if isinstance(other, Mint) else Mint(other)
        self *= other.inverse()
        return self
    def __floordiv__(self, other):
        new_obj = Mint(self.value)
        new_obj //= other
        return new_obj
    def __rfloordiv__(self, other):
        new_obj = Mint(Mint.get_value(other))
        new_obj //= self
        return new_obj

p=[]
i=0
while i<N:
    if S1[i]==S2[i]:
        p.append(1)
        i+=1
    else:
        p.append(0)
        i+=2
ans=Mint(1)
if p[0]==1: ans*=3
else: ans*=6
for i in range(1,len(p)):
    if p[i]==0:
        if p[i-1]==0:
            ans*=3
        else:
            ans*=2
    else:
        if p[i-1]==0:
            ans*=1
        else:
            ans*=2
print(ans)

Submission status: Accepted

Solution code:
N=int(input())
S1=input()
S2=input()
mod=10**9+7
ans=1
i=0
pretwo=False
while i<N:
    if i==0:
        if S1[i]!=S2[i]:
            ans*=6
            i+=2
            pretwo=True
        else:
            ans*=3
            i+=1
            pretwo=False
    else:
        if pretwo:
            if S1[i]!=S2[i]:
                ans*=3
                ans%=mod
                i+=2
                pretwo=True
            else:
                i+=1
                ans%=mod
                pretwo=False
        else:
            if S1[i]!=S2[i]:
                ans*=2
                ans%=mod
                i+=2
                pretwo=True
            else:
                ans*=2
                i+=1
                ans%=mod
                pretwo=False
print(ans)

Submission status: Accepted

Solution code:
N = int(input())
board = [input(), input()]

if N == 1:
    print(3)
    quit()


if board[0][0] == board[0][1]:
    cnt, prev = 6, 0
else:
    cnt, prev = 3, 1
mod = 10 ** 9 + 7

for i in range(1, N):
    if board[0][i] == board[0][i - 1]:
        continue
    elif i < N - 1 and board[0][i] == board[0][i + 1] and prev == 0:
        cnt *= 3
        cnt %= mod
    elif i < N - 1 and board[0][i] == board[0][i + 1] and prev == 1:
        cnt *= 2
        cnt %= mod
        prev = 0
    elif board[0][i] == board[1][i] and prev == 0:
        prev = 1
    else:
        cnt *= 2
        cnt %= mod
print(cnt)

Submission status: Accepted

Solution code:
n = int(input())
s1 = input()
s2 = input()
mod = 10**9+7
ans = 3
i = 0
j = -1
while i < n:
    if s1[i] == s2[i]:
        if j == 0:
            ans *= 2
        i += 1
        j = 0
    else:
        if j == 1:
            ans *= 3
        else:
            ans *= 2
        j = 1
        i += 2
    ans %= mod
print(ans)

Submission status: Accepted

Solution code:
N = int(input())
S = [input(), input()]

if S[0][0] == S[1][0]:
    ans = 3
    pre = 1
    skp = 0
else:
    ans = 6
    pre = 0
    skp = 1

mod = 10**9+7
for i in range(1,N):
    if skp:
        skp = 0
        continue
    if S[0][i] == S[1][i]:
        if pre:
            ans = ans*2%mod
        else:
            pre = 1
    else:
        skp = 1
        if pre:
            ans = ans*2%mod
            pre = 0
        else:
            ans = ans*3%mod
print(ans)

Submission status: Accepted

Solution code:
N = int(input())
MOD = 10**9 + 7
S = input() + "_"
T = input() + "_"
C = []
k = 0
while k < N:
    if S[k] == S[k+1]:
        C.append(2)
        k += 1
    else:
        C.append(1)
    k += 1
if C[0] == 1:
    ans = 3
else:
    ans = 6

for k in range(1,len(C)):
    if C[k-1] == 2 and C[k] == 2:
        ans *= 3
        ans %= MOD
    elif C[k-1] == 2 and C[k] == 1:
        ans *= 1
    elif C[k-1] == 1 and C[k] == 2:
        ans *= 2
        ans %= MOD
    else:
        ans *= 2
        ans %= MOD
print(ans)

Submission status: Accepted

Solution code:
N = int(input())
S = [list(input()) for _ in range(2)]

DIVIDER = 1000000007

c_type = []
i = 0
while i < N:
    if S[0][i] == S[1][i]:
        c_type.append(0)
        i += 1
    else:
        c_type.append(1)
        i += 2

for i in range(len(c_type)):
    if i == 0:
        ans = 3 if c_type[i] == 0 else 6
    elif c_type[i] == 0:
        if c_type[i - 1] == 0:
            ans = (ans * 2) % DIVIDER
        else:
            ans = (ans * 1) % DIVIDER
    else:
        if c_type[i - 1] == 0:
            ans = (ans * 2) % DIVIDER
        else:
            ans = (ans * 3) % DIVIDER

print(ans)

Submission status: Accepted

Solution code:
N = int(input())
s1 = input()
s2 = input()

MOD = 10**9+7
res = 1
flg = 2
idx = 0
while idx < N:
    if s1[idx] == s2[idx]:
        if flg==0:
            res *= 2
        elif flg==1:
            res *= 1
        else:
            res *= 3
        flg = 0
        idx += 1
    else:
        if flg==0:
            res *= 2
        elif flg==1:
            res *= 3
        else:
            res *= 6
        idx += 2
        flg = 1
print(res%MOD)

Submission status: Accepted

Solution code:
n = int(input())
s = str(input())
ss = str(input())
num = [1]

for i in range(n-1):
  if s[i] == s[i+1]:
    num[-1] += 1
  else:
    num.append(1)

ans = 1
status = 0
for i in range(len(num)):
  if num[i] == 2:
    if status == 1:
      ans *= 2
      status = 2
    elif status == 2:
      ans *= 3
    else:
      ans *= 6
      status = 2
  else:
    if status == 1:
      ans *= 2
    elif status == 2:
      status = 1
    else:
      ans *= 3
      status = 1
  ans %= 10 ** 9 + 7
print(ans)

Submission status: Accepted

Solution code:
MOD = 10 ** 9 + 7

N = int(input())

S1 = list(input())
S2 = list(input())

if S1[0] == S2[0]:
    flag = True #前が縦
    ans = 3
    i = 1
else:
    flag = False #前が横
    ans = 6
    i = 2

while i < N:
    if flag:
        if S1[i] == S2[i]: #縦のとき
            ans *= 2
            i += 1
        else:
            flag = False
            ans *= 2
            i += 2
    else:
        if S1[i] == S2[i]:
            flag = True
            i += 1
        else:
            ans *= 3
            i += 2
    ans %= MOD

print (ans)

Submission status: Accepted

Solution code:
import sys
mod = 1000000007

def solve():
    input = sys.stdin.readline
    N = int(input())
    U = input().strip("\n")
    D = input().strip("\n")
    DP = [0] * N
    if U[0] == D[0]: DP[0] = 3
    else: DP[0] = 6

    for i in range(1, N):
        if U[i] == U[i-1]:
            DP[i] = DP[i-1]
        else:
            if U[i-1] == D[i-1]: DP[i] = (DP[i-1] * 2) % mod
            else:
                if U[i] == D[i]: DP[i] = DP[i-1]
                else: DP[i] = (DP[i-1] * 3) % mod
    print(DP[N-1]) 


    return 0

if __name__ == "__main__":
    solve()

Submission status: Accepted

Solution code:
N = int(input())
S = input()
T = input()
MOD = 10**9+7

ans = 3
if S[0] != T[0]:
    ans *= 2
for s1,t1,s2,t2 in zip(S,T,S[1:],T[1:]):
    if s1==s2 and t1==t2: continue
    if s1==t1:
        ans *= 2
    elif s2!=t2:
        ans *= 3
print(ans%MOD)

Submission status: Accepted

Solution code:
N = int(input())
S = input()
T = input()
MOD = 10**9 + 7

isPrevI = S[0] == T[0]
i = 1 if isPrevI else 2
ans = 3 if isPrevI else 6

while i < N:
    if S[i] == T[i]:
        if isPrevI:
            ans *= 2
            ans %= MOD
        isPrevI = True
        i += 1
    else:
        if isPrevI:
            ans *= 2
            ans %= MOD
        else:
            ans *= 3
            ans %= MOD
        isPrevI = False
        i += 2

print(ans)