제출 #87724

#제출 시각아이디문제언어결과실행 시간메모리
87724JustInCaseBitaro’s Party (JOI18_bitaro)C++17
7 / 100
2048 ms15796 KiB
/** Solution: Idea: We can precompute for each node the sqrt(n) furthest nodes with a simple dp. Then for each query if the number of forbidden nodes is less than sqrt(n) then for sure the answer will be among the precomputed otherwise we can simply solve it with a brutefore since the queries of this type will be less than sqrt(n). */ #include <bits/stdc++.h> const int32_t MAX_N = 1e5; const int32_t BUCKET_SIZE = 150; bool isForbidden[MAX_N + 5]; class Graph { private: struct Node { int32_t id; std::vector< std::pair< int32_t, int32_t > > dp; std::vector< Node* > v, rev; }; int32_t cntNodes; Node nodes[MAX_N + 5]; public: void Init(int32_t _cntNodes) { cntNodes = _cntNodes; for(int32_t i = 1; i <= cntNodes; i++) { nodes[i].id = i; } } void AddEdge(int32_t from, int32_t to) { nodes[from].v.push_back(&nodes[to]); nodes[to].rev.push_back(&nodes[from]); } void Precompute() { for(int32_t i = 1; i <= cntNodes; i++) { std::vector< std::pair< int32_t, int32_t > > dists; dists.push_back({ 0, i }); for(auto &x : nodes[i].v) { for(auto &y : x->dp) { dists.push_back({ y.first + 1, y.second }); } } std::sort(dists.begin(), dists.end()); for(int32_t j = dists.size() - 1; j >= 0; j--) { if(nodes[i].dp.size() == 0 || nodes[i].dp.back().second != dists[j].second) { nodes[i].dp.push_back(dists[j]); if(nodes[i].dp.size() == BUCKET_SIZE) { break; } } } } } int32_t SolveSmallK(int32_t t) { for(auto &x : nodes[t].dp) { if(!isForbidden[x.second]) { return x.first; } } return -1; } int32_t SolveBigK(int32_t t) { std::vector< int32_t > dp(t + 1, 0); int32_t ans = (isForbidden[t] ? -1 : 0); for(int32_t i = t - 1; i >= 1; i--) { bool isChanged = false; for(auto &x : nodes[i].rev) { if(x->id <= t && (x->id == t || dp[x->id] != 0)) { dp[i] = std::max(dp[i], dp[x->id] + 1); isChanged = true; } } if(isChanged && !isForbidden[i]) { ans = std::max(ans, dp[i]); } } return ans; } }; Graph g; int main() { std::ios_base::sync_with_stdio(false); std::cin.tie(nullptr); int32_t n, m, q; std::cin >> n >> m >> q; g.Init(n); for(int32_t i = 0; i < m; i++) { int32_t u, v; std::cin >> u >> v; g.AddEdge(v, u); } g.Precompute(); for(int32_t i = 0; i < q; i++) { int32_t t, k; std::cin >> t >> k; std::vector< int32_t > c(k); for(int32_t j = 0; j < k; j++) { std::cin >> c[j]; isForbidden[c[j]] = true; } if(k >= BUCKET_SIZE) { std::cout << g.SolveBigK(t) << '\n'; } else { std::cout << g.SolveSmallK(t) << '\n'; } for(int32_t j = 0; j < k; j++) { isForbidden[c[j]] = false; } } }
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...