test/yosupo/number_of_subsequences.test.cpp

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Last update: 2024-01-07 23:25:49+09:00
Problem: https://judge.yosupo.jp/problem/number_of_subsequences

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Code

#define PROBLEM "https://judge.yosupo.jp/problem/number_of_subsequences"

#include "../../math/modint.hpp"
#include "../../data-structure/fenwick_tree.hpp"

#include <bits/stdc++.h>
using namespace std;

using mint = Modint<998244353>;

struct AddMonoid {
    using T = mint;
    static T id() { return 0; }
    static T op(T a, T b) {
        return a + b;
    }
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int N;
    cin >> N;
    vector<int> A(N);
    for (auto& x : A) cin >> x;
    map<int, int> last;
    FenwickTree<AddMonoid> ft(N+1);
    ft.update(0, 1);
    for (int i = 0; i < N; ++i) {
        int l = last[A[i]];
        ft.update(i+1, ft.prefix_fold(i+1) - ft.prefix_fold(l));
        last[A[i]] = i + 1;
    }
    cout << ft.prefix_fold(N + 1) - 1 << endl;
}

#line 1 "test/yosupo/number_of_subsequences.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/number_of_subsequences"

#line 2 "math/modint.hpp"
#include <algorithm>
#include <iostream>

/**
 * @brief Mod int
 */
template <int m>
class Modint {
    using mint = Modint;
    static_assert(m > 0, "Modulus must be positive");

   public:
    static constexpr int mod() { return m; }

    constexpr Modint(long long y = 0) : x(y >= 0 ? y % m : (y % m + m) % m) {}

    constexpr int val() const { return x; }

    constexpr mint& operator+=(const mint& r) {
        if ((x += r.x) >= m) x -= m;
        return *this;
    }
    constexpr mint& operator-=(const mint& r) {
        if ((x += m - r.x) >= m) x -= m;
        return *this;
    }
    constexpr mint& operator*=(const mint& r) {
        x = static_cast<int>(1LL * x * r.x % m);
        return *this;
    }
    constexpr mint& operator/=(const mint& r) { return *this *= r.inv(); }

    constexpr bool operator==(const mint& r) const { return x == r.x; }

    constexpr mint operator+() const { return *this; }
    constexpr mint operator-() const { return mint(-x); }

    constexpr friend mint operator+(const mint& l, const mint& r) {
        return mint(l) += r;
    }
    constexpr friend mint operator-(const mint& l, const mint& r) {
        return mint(l) -= r;
    }
    constexpr friend mint operator*(const mint& l, const mint& r) {
        return mint(l) *= r;
    }
    constexpr friend mint operator/(const mint& l, const mint& r) {
        return mint(l) /= r;
    }

    constexpr mint inv() const {
        int a = x, b = m, u = 1, v = 0;
        while (b > 0) {
            int t = a / b;
            std::swap(a -= t * b, b);
            std::swap(u -= t * v, v);
        }
        return mint(u);
    }

    constexpr mint pow(long long n) const {
        mint ret(1), mul(x);
        while (n > 0) {
            if (n & 1) ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }

    friend std::ostream& operator<<(std::ostream& os, const mint& r) {
        return os << r.x;
    }

    friend std::istream& operator>>(std::istream& is, mint& r) {
        long long t;
        is >> t;
        r = mint(t);
        return is;
    }

   private:
    int x;
};
#line 2 "data-structure/fenwick_tree.hpp"
#include <functional>
#include <vector>

template <typename M>
class FenwickTree {
    using T = M::T;

   public:
    FenwickTree() = default;
    explicit FenwickTree(int n) : n(n), data(n + 1, M::id()) {}

    T prefix_fold(int i) const {
        T ret = M::id();
        for (; i > 0; i -= i & -i) ret = M::op(ret, data[i]);
        return ret;
    }

    void update(int i, const T& x) {
        for (++i; i <= n; i += i & -i) data[i] = M::op(data[i], x);
    }

    int lower_bound(const T& x) const { return lower_bound(x, std::less<>()); }

    template <typename Compare>
    int lower_bound(const T& x, Compare cmp) const {
        if (!cmp(M::id(), x)) return 0;
        int k = 1;
        while (k * 2 <= n) k <<= 1;
        int i = 0;
        T v = M::id();
        for (; k > 0; k >>= 1) {
            if (i + k > n) continue;
            T nv = M::op(v, data[i + k]);
            if (cmp(nv, x)) {
                v = nv;
                i += k;
            }
        }
        return i + 1;
    }

   private:
    int n;
    std::vector<T> data;
};
#line 5 "test/yosupo/number_of_subsequences.test.cpp"

#include <bits/stdc++.h>
using namespace std;

using mint = Modint<998244353>;

struct AddMonoid {
    using T = mint;
    static T id() { return 0; }
    static T op(T a, T b) {
        return a + b;
    }
};

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int N;
    cin >> N;
    vector<int> A(N);
    for (auto& x : A) cin >> x;
    map<int, int> last;
    FenwickTree<AddMonoid> ft(N+1);
    ft.update(0, 1);
    for (int i = 0; i < N; ++i) {
        int l = last[A[i]];
        ft.update(i+1, ft.prefix_fold(i+1) - ft.prefix_fold(l));
        last[A[i]] = i + 1;
    }
    cout << ft.prefix_fold(N + 1) - 1 << endl;
}