Submission #1031304

#TimeUsernameProblemLanguageResultExecution timeMemory
1031304stdfloatBoat (APIO16_boat)C++17
9 / 100
1338 ms1772 KiB
#include <bits/stdc++.h> using namespace std; using ll = long long; #define sz(v) (int)(v).size() const int md = (int)1e9 + 7; const int N = (int)1e5 + 1; vector<int> fct(N), inv(N), inv_fct(N); int pw(int x, int y) { int res = 1; while (y) { if (y & 1) res = (ll)res * x % md; x = (ll)x * x % md; y >>= 1; } return res; } int C(int n, int r) { int x = 1; for (int i = 1; i <= r; i++) x = (ll)x * (n - r + i) % md; return (ll)x * inv_fct[r] % md; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); fct[0] = inv[0] = inv_fct[0] = 1; for (int i = 1; i < N; i++) { inv[i] = pw(i, md - 2); fct[i] = (ll)fct[i - 1] * i % md; inv_fct[i] = pw(fct[i], md - 2); } int n; cin >> n; map<int, vector<int>> m; vector<int> a(n + 1), b(n + 1); for (int i = 1; i <= n; i++) { cin >> a[i] >> b[i]; m[a[i]].push_back(i); m[b[i] + 1].push_back(-i); } vector<int> mv; for (auto i : m) mv.push_back(i.first); set<int> s; vector<int> dp(n + 1); for (int ii = 0; ii + 1 < sz(mv); ii++) { for (auto j : m[mv[ii]]) { if (0 < j) s.insert(j); else s.erase(-j); } int R = mv[ii + 1] - mv[ii]; vector<int> v(s.begin(), s.end()), nw_dp = dp; for (int i = 0; i < sz(v); i++) { int sm = 1; for (int j = 1; j < v[i]; j++) sm = (sm + dp[j]) % md; nw_dp[v[i]] = (dp[v[i]] + (ll)sm * R % md) % md; vector<int> p(n); for (int j = 0; j < n; j++) p[j] = ((j ? p[j - 1] : 0) + dp[j]) % md; for (int j = 1; j <= min(i, R - 1); j++) { int c = C(R, j + 1), x = fct[j - 1]; // cout << "\nj " << j << ' ' << x << '\n'; for (int k = i - j; k >= 0; k--) { int pre = ((v[k] ? p[v[k] - 1] : 0) + 1) % md; if (k != i - j) x = (ll)x * (i - k - 1) * inv[i - k - j] % md; nw_dp[v[i]] = (nw_dp[v[i]] + ((ll)pre * ((ll)x * inv_fct[j - 1] % md) % md) * c % md) % md; // cout << i - k - 1 << ' ' << j - 1 << ' ' << x << ' ' << (ll)x * inv_fct[j - 1] % md << ' ' << C(i - k - 1, j - 1) << '\n'; } } } dp = nw_dp; } int sm = 0; for (auto i : dp) sm = (sm + i) % md; cout << sm << '\n'; }
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