/* * Opis: Główny nagłówek */ #include<bits/stdc++.h> using namespace std; using LL=long long; using D=long double; #define FOR(i,l,r)for(int i=(l);i<=(r);++i) #define REP(i,n)FOR(i,0,(n)-1) #define ssize(x)int(x.size()) #ifdef DEBUG auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";} auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";} #define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X) #else #define debug(...){} #endif constexpr int W = 2000; constexpr int N = 5e4; void generate_example(int& n, int& t, vector<D>& arr) { n = N; t = N / 2; arr.resize(n, 1./2); } int main() { cin.tie(0)->sync_with_stdio(0); int n, t; //vector<D> arr; // generate_example(n, t, arr); cin >> n >> t; vector<D> arr(n); for (auto& v : arr) { cin >> v; } sort(arr.begin(), arr.end()); reverse(arr.begin(), arr.end()); D res = 0; D mid = 0; vector<pair<int, D>> dp, temp; // every 2 dp.reserve(4*W); temp.reserve(4*W); dp.push_back({0, 1}); for (D p: arr) { D q = 1-p; mid += 2*p - 1; temp.push_back(dp.front()); temp.front().first--; temp.front().second *= q; temp.resize(ssize(dp) + 1); FOR(i, 1, ssize(dp)-1) { temp[i].first = dp[i].first - 1; temp[i].second = p * dp[i-1].second + q * dp[i].second; } temp.back() = dp.back(); temp.back().first++; temp.back().second *= p; D curr_res = 0; for (auto [wh, pr] : temp) { if (wh >= t) { curr_res += pr; } } res = max(res, curr_res); int mid_int = (int) mid; dp.clear(); for (auto [wh, pr] : temp) { if (abs(wh - mid_int) <= W) { dp.push_back({wh, pr}); } } temp.clear(); } cout << fixed << setprecision(9) << res << "\n"; }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 | /* * Opis: Główny nagłówek */ #include<bits/stdc++.h> using namespace std; using LL=long long; using D=long double; #define FOR(i,l,r)for(int i=(l);i<=(r);++i) #define REP(i,n)FOR(i,0,(n)-1) #define ssize(x)int(x.size()) #ifdef DEBUG auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";} auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";} #define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X) #else #define debug(...){} #endif constexpr int W = 2000; constexpr int N = 5e4; void generate_example(int& n, int& t, vector<D>& arr) { n = N; t = N / 2; arr.resize(n, 1./2); } int main() { cin.tie(0)->sync_with_stdio(0); int n, t; //vector<D> arr; // generate_example(n, t, arr); cin >> n >> t; vector<D> arr(n); for (auto& v : arr) { cin >> v; } sort(arr.begin(), arr.end()); reverse(arr.begin(), arr.end()); D res = 0; D mid = 0; vector<pair<int, D>> dp, temp; // every 2 dp.reserve(4*W); temp.reserve(4*W); dp.push_back({0, 1}); for (D p: arr) { D q = 1-p; mid += 2*p - 1; temp.push_back(dp.front()); temp.front().first--; temp.front().second *= q; temp.resize(ssize(dp) + 1); FOR(i, 1, ssize(dp)-1) { temp[i].first = dp[i].first - 1; temp[i].second = p * dp[i-1].second + q * dp[i].second; } temp.back() = dp.back(); temp.back().first++; temp.back().second *= p; D curr_res = 0; for (auto [wh, pr] : temp) { if (wh >= t) { curr_res += pr; } } res = max(res, curr_res); int mid_int = (int) mid; dp.clear(); for (auto [wh, pr] : temp) { if (abs(wh - mid_int) <= W) { dp.push_back({wh, pr}); } } temp.clear(); } cout << fixed << setprecision(9) << res << "\n"; } |