#ifndef ATCODER_DSU_HPP #define ATCODER_DSU_HPP 1 #include #include #include namespace atcoder { // Implement (union by size) + (path compression) // Reference: // Zvi Galil and Giuseppe F. Italiano, // Data structures and algorithms for disjoint set union problems struct dsu { public: dsu() : _n(0) {} dsu(int n) : _n(n), parent_or_size(n, -1) {} int merge(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); int x = leader(a), y = leader(b); if (x == y) return x; if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y); parent_or_size[x] += parent_or_size[y]; parent_or_size[y] = x; return x; } bool same(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); return leader(a) == leader(b); } int leader(int a) { assert(0 <= a && a < _n); if (parent_or_size[a] < 0) return a; return parent_or_size[a] = leader(parent_or_size[a]); } int size(int a) { assert(0 <= a && a < _n); return -parent_or_size[leader(a)]; } std::vector> groups() { std::vector leader_buf(_n), group_size(_n); for (int i = 0; i < _n; i++) { leader_buf[i] = leader(i); group_size[leader_buf[i]]++; } std::vector> result(_n); for (int i = 0; i < _n; i++) { result[i].reserve(group_size[i]); } for (int i = 0; i < _n; i++) { result[leader_buf[i]].push_back(i); } result.erase(std::remove_if( result.begin(), result.end(), [&](const std::vector& v) { return v.empty(); }), result.end()); return result; } private: int _n; // root node: -1 * component size // otherwise: parent std::vector parent_or_size; }; } // namespace atcoder #endif // ATCODER_DSU_HPP #include using namespace std; using namespace atcoder; int main() { int n, q; cin >> n >> q; vector p(n); dsu uf(n); for (int i = 0; i < n; i++) { cin >> p[i]; p[i]--; if (p[i] >= 0) { uf.merge(i, p[i]); } } for (; q--;) { int a, b; cin >> a >> b; a--; b--; if (uf.same(a, b)) { cout << "Yes" << endl; } else { cout << "No" << endl; } } }