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View the Project on GitHub Luzhiled/syakyo-library
// verification-helper: PROBLEM https://atcoder.jp/contests/arc117/tasks/arc117_c #include "src/math/modular-arithmetic/small-mod-combination.hpp" #include "src/math/modular-arithmetic/static-modint.hpp" #include <iostream> #include <string> namespace luz { void main_() { using mint = StaticPrimeModInt< 3 >; SmallModCombination< mint > mc; usize n; std::cin >> n; std::string s; std::cin >> s; auto convert = [](char c) { switch (c) { case 'B': return 0; case 'W': return 1; case 'R': return 2; default: exit(-1); } }; mint sum; for (usize i = 0; i < n; i++) { sum += (n & 1 ? 1 : -1) * convert(s[i]) * mc.combination(n - 1, i); } auto inverse = [](mint x) { switch (x.val()) { case 0: return 'B'; case 1: return 'W'; case 2: return 'R'; default: exit(-1); } }; std::cout << inverse(sum) << std::endl; } } // namespace luz int main() { luz::main_(); }
#line 1 "test/atcoder/arc117_c.test.cpp" // verification-helper: PROBLEM https://atcoder.jp/contests/arc117/tasks/arc117_c #line 2 "src/math/modular-arithmetic/small-mod-combination.hpp" #line 2 "src/math/modular-arithmetic/modular-combinatorics.hpp" #line 2 "src/cpp-template/header/size-alias.hpp" #include <cstddef> namespace luz { using isize = std::ptrdiff_t; using usize = std::size_t; } #line 4 "src/math/modular-arithmetic/modular-combinatorics.hpp" #include <vector> namespace luz { template < typename mint > class Combinatorics { static usize bound; static std::vector< mint > fact, finv, inv; static void expand(usize n) { n += 1; if (fact.size() >= n) return; if (bound == 0) bound = 1; fact.resize(n, mint(1)); finv.resize(n, mint(1)); inv.resize(n, mint(1)); for (usize i = bound; i < n; i++) { fact[i] = fact[i - 1] * i; } finv.back() = mint(1) / fact.back(); for (usize i = n - 1; i >= bound; i--) { finv[i - 1] = finv[i] * i; } for (usize i = bound; i < n; i++) { inv[i] = finv[i] * fact[i - 1]; } bound = n; } public: explicit Combinatorics(usize n = 0) { expand(n); } static mint factorial(usize n) { expand(n); return fact[n]; } static mint factorial_inverse(usize n) { expand(n); return finv[n]; } static mint inverse(usize n) { expand(n); return inv[n]; } static mint permutation(isize n, isize r) { if (r < 0 or n < r) return 0; expand(n); return fact[n] * finv[n - r]; } static mint combination(isize n, isize r) { if (r < 0 or n < r) return 0; expand(n); return fact[n] * finv[r] * finv[n - r]; } static mint combination_with_repetitions(isize n, isize r) { if (n < 0 or r < 0) return 0; return (r ? combination(n + r - 1, r) : 1); } static mint P(isize n, isize r) { return permutation(n, r); } static mint C(isize n, isize r) { return combination(n, r); } static mint H(isize n, isize r) { return combination_with_repetitions(n, r); } }; template < typename mint > usize Combinatorics< mint >::bound = 0; template < typename mint > std::vector< mint > Combinatorics< mint >::fact = std::vector< mint >(); template < typename mint > std::vector< mint > Combinatorics< mint >::finv = std::vector< mint >(); template < typename mint > std::vector< mint > Combinatorics< mint >::inv = std::vector< mint >(); } // namespace luz #line 4 "src/math/modular-arithmetic/small-mod-combination.hpp" namespace luz { template < typename modint > class SmallModCombination { static constexpr auto mod = modint::get_mod(); Combinatorics< modint > mc; public: SmallModCombination(): mc(mod - 1) {} modint combination(isize n, isize r) { if (r < 0 or n < r) return 0; modint result(1); while (n) { result *= mc.combination(n % mod, r % mod); n /= mod; r /= mod; } return result; } modint C(isize n, isize r) { return combination(n, r); } }; } // namespace luz #line 2 "src/math/modular-arithmetic/static-modint.hpp" #line 2 "src/cpp-template/header/int-alias.hpp" #include <cstdint> namespace luz { using i32 = std::int32_t; using i64 = std::int64_t; using u32 = std::uint32_t; using u64 = std::uint64_t; } #line 4 "src/math/modular-arithmetic/static-modint.hpp" #include <cassert> #include <iostream> namespace luz { template < u32 mod > class StaticPrimeModInt { using modint = StaticPrimeModInt; u32 v; public: StaticPrimeModInt(): v(0) {} template < typename T > StaticPrimeModInt(T t) { i64 x = (i64)(t % (i64)mod); if (x < 0) x += mod; v = (u32)x; } u32 val() const { return v; } modint &operator+=(const modint &rhs) { v += rhs.v; if (v >= mod) v -= mod; return *this; } modint &operator-=(const modint &rhs) { v += mod - rhs.v; // <- if (v >= mod) v -= mod; return *this; } modint &operator*=(const modint &rhs) { v = (u32)(u64(1) * v * rhs.v % mod); return *this; } modint &operator/=(const modint &rhs) { *this *= rhs.inverse(); return *this; } modint operator+() const { return *this; } modint operator-() const { return modint() - *this; } friend modint operator+(const modint &lhs, const modint &rhs) { return modint(lhs) += rhs; } friend modint operator-(const modint &lhs, const modint &rhs) { return modint(lhs) -= rhs; } friend modint operator*(const modint &lhs, const modint &rhs) { return modint(lhs) *= rhs; } friend modint operator/(const modint &lhs, const modint &rhs) { return modint(lhs) /= rhs; } friend bool operator==(const modint &lhs, const modint &rhs) { return lhs.v == rhs.v; } friend bool operator!=(const modint &lhs, const modint &rhs) { return lhs.v != rhs.v; } modint pow(i64 n) const { assert(0 <= n); modint x = *this, r = 1; while (n) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; } modint inverse() const { assert(v != 0); return pow(mod - 2); } static constexpr u32 get_mod() { return mod; } friend std::ostream &operator<<(std::ostream &os, const modint &m) { os << m.val(); return os; } }; using modint998244353 = StaticPrimeModInt< 998244353 >; using modint1000000007 = StaticPrimeModInt< 1000000007 >; } // namespace luz #line 5 "test/atcoder/arc117_c.test.cpp" #line 7 "test/atcoder/arc117_c.test.cpp" #include <string> namespace luz { void main_() { using mint = StaticPrimeModInt< 3 >; SmallModCombination< mint > mc; usize n; std::cin >> n; std::string s; std::cin >> s; auto convert = [](char c) { switch (c) { case 'B': return 0; case 'W': return 1; case 'R': return 2; default: exit(-1); } }; mint sum; for (usize i = 0; i < n; i++) { sum += (n & 1 ? 1 : -1) * convert(s[i]) * mc.combination(n - 1, i); } auto inverse = [](mint x) { switch (x.val()) { case 0: return 'B'; case 1: return 'W'; case 2: return 'R'; default: exit(-1); } }; std::cout << inverse(sum) << std::endl; } } // namespace luz int main() { luz::main_(); }