// https://yukicoder.me/problems/no/2319 // really cool problem // // Solution 0. use bitsets and bruteforce // // Solution 1. sqrt over nodes // let K = sqrt(M) // a person is "few" if it has < K friends and "many" if >= K // there are at most 2M / K ~= K people that are "many" // to solve a query where x is few, brute force it // to solve a query where x is many, consider its friends that are: // a. many - you can check ALL many's for the condition // b. few - store this as map f[i][j] = # of few friends of the many i in world j // update naively, it works in O(Q*sqrt M + N*sqrt M + M) // // Solution 2. sqrt over queries #include #pragma GCC optimize("Ofast,unroll-loops,strict-overflow") #pragma GCC target("avx2") using namespace std; using HashSet = unordered_set; using FewCounter = unordered_map>; // signed main2() { // cout << "sol 1\n"; // freopen("/Users/drymerge/CLionProjects/DEBUG/a.in", "r", stdin); // freopen("/Users/drymerge/a.out", "w", stdout); // cin.tie(0)->sync_with_stdio(0); // int N, M, Q; // cin >> N >> M; // int K = sqrt(M); // vector world(N+1); // world[i] = the world that person i is in // FewCounter num_few_of; // num_few_of[i].at(w) = # friends of i in world j with < K friends // vector many; // many = [those with >= K friends] // vector friends(N+1); // auto is_many = [&] (int i) { // return friends[i].size() >= K; // }; // for (int i = 1; i <= N; ++i) // cin >> world[i]; // for (int i = 1; i <= M; ++i) { // int a, b; // cin >> a >> b; // friends[a].insert(b); // friends[b].insert(a); // } // for (int i = 1; i <= N; ++i) { // if (!is_many(i)) continue; // many.push_back(i); // num_few_of[i].assign(N+1, 0); // for (int f : friends[i]) // if (!is_many(f)) { // int w = world[f]; // ++num_few_of[i].at(w); // } // } // auto solve_many = [&] (int x, int y) { // int new_world = world[y]; // if (num_few_of[x].at(new_world) > 0) // goto success; // for (int m : many) // if (friends[x].count(m) && world[m] == new_world) // goto success; // return "No\n"; // success: // world[x] = new_world; // return "Yes\n"; // }; // auto solve_few = [&] (int x, int y) { // for (int f : friends[x]) // if (world[f] == world[y]) // goto success; // return "No\n"; // success: // int old_world = world[x]; // int new_world = world[y]; // for (int f : friends[x]) { // if (!is_many(f)) continue; // --num_few_of[f].at(old_world); // ++num_few_of[f].at(new_world); // } // world[x] = new_world; // return "Yes\n"; // }; // cin >> Q; // while (Q--) { // int x, y; // cin >> x >> y; // if (world[x] == world[y]) { // cout << "No\n"; // continue; // } // auto ans = is_many(x) ? solve_many(x,y) : solve_few(x,y); // cout << ans; // } // } #include using namespace __gnu_pbds; constexpr size_t MXN = 20001; constexpr size_t MXM = 400000; // constexpr size_t MXN = 100; // constexpr size_t MXM = 100; signed main() { // cout << "sol2\n"; // freopen("/Users/drymerge/CLionProjects/DEBUG/a.in", "r", stdin); // freopen("/Users/drymerge/b.out", "w", stdout); cin.tie(0)->sync_with_stdio(0); int N, M, Q; cin >> N >> M; short world[MXN]; bitset friends[MXN]; short friendships[MXM]; gp_hash_table initial_count[MXN]; // initial_count[i][j] = # of friends of i in world j for (int i = 1; i <= N; ++i) cin >> world[i]; for (int i = 0; i < M; ++i) { short a, b; cin >> a >> b; friendships[2*i] = a, friendships[2*i+1] = b; friends[a][b] = true; friends[b][a] = true; } auto reset_map = [&] { for (int i = 1; i <= N; ++i) initial_count[i].clear(); for (int i = 0; i < M; ++i) { short a = friendships[2*i]; short b = friendships[2*i+1]; ++initial_count[a][world[b]]; ++initial_count[b][world[a]]; } }; cin >> Q; int K = sqrt(Q); int q = 0; vector> succeeded; succeeded.reserve(K); while (q < Q) { reset_map(); for (int k = 0; k < K && q < Q; ++k, ++q) { short x, y; cin >> x >> y; if (world[x] == world[y]) { cout << "No\n"; continue; } int start = initial_count[x][world[y]]; for (auto [xl,yl,wx,wy] : succeeded) { if (wx == world[y] && friends[x][xl]) --start; if (wy == world[y] && friends[x][xl]) ++start; } if (start > 0) { cout << "Yes\n"; succeeded.push_back( {x,y,world[x],world[y]} ); world[x] = world[y]; } else cout << "No\n"; } succeeded.resize(0); } return 0; }