sotanishy's code snippets for competitive programming
View the Project on GitHub sotanishy/cp-library-cpp
#define PROBLEM "https://judge.yosupo.jp/problem/lca" #include "../../tree/lca.hpp" #include <bits/stdc++.h> using namespace std; using ll = long long; int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int N, Q; cin >> N >> Q; vector<vector<int>> G(N); for (int i = 1; i < N; ++i) { int p; cin >> p; G[p].push_back(i); } LCA lca(G, 0); for (int i = 0; i < Q; ++i) { int u, v; cin >> u >> v; cout << lca.query(u, v) << "\n"; } }
#line 1 "test/yosupo/lca.test.cpp" #define PROBLEM "https://judge.yosupo.jp/problem/lca" #line 2 "tree/lca.hpp" #include <algorithm> #include <bit> #include <vector> class LCA { public: LCA() = default; LCA(const std::vector<std::vector<int>>& G, int root) : G(G), LOG(std::bit_width(G.size())), depth(G.size()), table(LOG, std::vector<int>(G.size(), -1)) { dfs(root, -1, 0); for (int k = 0; k < LOG - 1; ++k) { for (int v = 0; v < (int)G.size(); ++v) { if (table[k][v] >= 0) { table[k + 1][v] = table[k][table[k][v]]; } } } } int query(int u, int v) const { if (depth[u] > depth[v]) std::swap(u, v); // go up to the same depth for (int k = 0; k < LOG; ++k) { if ((depth[v] - depth[u]) >> k & 1) { v = table[k][v]; } } if (u == v) return u; for (int k = LOG - 1; k >= 0; --k) { if (table[k][u] != table[k][v]) { u = table[k][u]; v = table[k][v]; } } return table[0][u]; } int dist(int u, int v) const { return depth[u] + depth[v] - 2 * depth[query(u, v)]; } int parent(int v, int k) const { for (int i = LOG - 1; i >= 0; --i) { if (k >= (1 << i)) { v = table[i][v]; k -= 1 << i; } } return v; } int jump(int u, int v, int k) const { int l = query(u, v); int du = depth[u] - depth[l]; int dv = depth[v] - depth[l]; if (du + dv < k) return -1; if (k < du) return parent(u, k); return parent(v, du + dv - k); } protected: const std::vector<std::vector<int>>& G; const int LOG; std::vector<int> depth; std::vector<std::vector<int>> table; void dfs(int v, int p, int d) { table[0][v] = p; depth[v] = d; for (int c : G[v]) { if (c != p) dfs(c, v, d + 1); } } }; #line 4 "test/yosupo/lca.test.cpp" #include <bits/stdc++.h> using namespace std; using ll = long long; int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int N, Q; cin >> N >> Q; vector<vector<int>> G(N); for (int i = 1; i < N; ++i) { int p; cin >> p; G[p].push_back(i); } LCA lca(G, 0); for (int i = 0; i < Q; ++i) { int u, v; cin >> u >> v; cout << lca.query(u, v) << "\n"; } }