114 lines
2.2 KiB
C++
114 lines
2.2 KiB
C++
#include <bits/stdc++.h> // {{{
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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using i32 = int32_t;
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using u32 = uint32_t;
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using i64 = int64_t;
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using u64 = uint64_t;
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using d64 = double;
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using d128 = long double;
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template <typename T>
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using vec = std::vector<T>;
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template <typename T, size_t N>
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using arr = std::array<T, N>;
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template <typename T1, typename T2>
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using pai = std::pair<T1, T2>;
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template <typename T>
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constexpr T MIN = std::numeric_limits<T>::min();
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template <typename T>
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constexpr T MAX = std::numeric_limits<T>::max();
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template <typename T>
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[[nodiscard]] static T sc(auto&& x) {
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return static_cast<T>(x);
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}
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template <typename T>
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[[nodiscard]] static T sz(auto&& x) {
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return static_cast<T>(x.size());
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}
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static void NO() {
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std::cout << "NO\n";
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}
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static void YES() {
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std::cout << "YES\n";
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}
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#define all(x) (x).begin(), (x).end()
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#define rall(x) (x).rbegin(), (x).rend()
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#ifdef LOCAL
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#define db(...) std::print(__VA_ARGS__)
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#define dbln(...) std::println(__VA_ARGS__)
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#else
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#define db(...)
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#define dbln(...)
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#endif
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// }}}
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static constexpr u64 MOD = 1e9 + 7;
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void solve() {
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u32 n, m;
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cin >> n >> m;
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vec<i64> a(n);
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for (auto& e : a)
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cin >> e;
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vec<i64> prev(m + 1, 0);
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if (a[0] != 0) {
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prev[a[0]] = 1;
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} else {
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for (u32 i = 1; i <= m; ++i)
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prev[i] = 1;
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}
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for (u32 i = 2; i <= n; ++i) {
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vec<i64> cur(m + 1, 0);
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if (a[i - 1] == 0) {
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for (u32 x = 1; x <= m; ++x) {
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for (i64 delta = -1; delta <= 1; ++delta) {
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if (1 <= x + delta && x + delta <= m)
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cur[x] = (cur[x] + prev[x + delta]) % MOD;
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}
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}
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} else {
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for (i64 delta = -1; delta <= 1; ++delta) {
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if (1 <= a[i - 1] + delta && a[i - 1] + delta <= m)
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cur[a[i - 1]] = (cur[a[i - 1]] + prev[a[i - 1] + delta]) % MOD;
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}
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}
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prev = cur;
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}
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i64 ans = 0;
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for (auto e : prev) {
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ans = (ans + e) % MOD;
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}
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cout << ans << '\n';
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}
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int main() { // {{{
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cin.tie(nullptr)->sync_with_stdio(false);
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cin.exceptions(cin.failbit);
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int tc = 1;
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// cin >> tc;
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for (int t = 0; t < tc; ++t) {
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solve();
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}
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return 0;
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}
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// }}}
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