This documentation is automatically generated by online-judge-tools/verification-helper
#include "graph/tree/offline-lca.hpp"
#include "../graph-template.hpp"
#include "../../structure/union-find/union-find.hpp"
/**
* @brief Offline LCA(オフライン最小共通祖先)
**/
template< typename T >
vector< int > offline_lca(const Graph< T > &g, vector< pair< int, int > > &qs, int root = 0) {
int n = (int) g.size();
UnionFind uf(n);
vector< int > st(n), mark(n), ptr(n), ans(qs.size(), -1);
int top = 0;
st[top] = root;
for(auto&[l, r]: qs) mark[l]++, mark[r]++;
vector< vector< pair< int, int > > > q(n);
for(int i = 0; i < n; i++) {
q[i].reserve(mark[i]);
mark[i] = -1;
ptr[i] = (int) g[i].size();
}
for(int i = 0; i < qs.size(); i++) {
q[qs[i].first].emplace_back(qs[i].second, i);
q[qs[i].second].emplace_back(qs[i].first, i);
}
auto run = [&](int u) -> bool {
while(ptr[u]) {
int v = g[u][--ptr[u]];
if(mark[v] == -1) {
st[++top] = v;
return true;
}
}
return false;
};
while(~top) {
int u = st[top];
if(mark[u] == -1) {
mark[u] = u;
} else {
uf.unite(u, g[u][ptr[u]]);
mark[uf.find(u)] = u;
}
if(not run(u)) {
for(auto&[v, i]: q[u]) {
if(~mark[v] and ans[i] == -1) {
ans[i] = mark[uf.find(v)];
}
}
--top;
}
}
return ans;
}
#line 2 "graph/graph-template.hpp"
/**
* @brief Graph Template(グラフテンプレート)
*/
template< typename T = int >
struct Edge {
int from, to;
T cost;
int idx;
Edge() = default;
Edge(int from, int to, T cost = 1, int idx = -1) : from(from), to(to), cost(cost), idx(idx) {}
operator int() const { return to; }
};
template< typename T = int >
struct Graph {
vector< vector< Edge< T > > > g;
int es;
Graph() = default;
explicit Graph(int n) : g(n), es(0) {}
size_t size() const {
return g.size();
}
void add_directed_edge(int from, int to, T cost = 1) {
g[from].emplace_back(from, to, cost, es++);
}
void add_edge(int from, int to, T cost = 1) {
g[from].emplace_back(from, to, cost, es);
g[to].emplace_back(to, from, cost, es++);
}
void read(int M, int padding = -1, bool weighted = false, bool directed = false) {
for(int i = 0; i < M; i++) {
int a, b;
cin >> a >> b;
a += padding;
b += padding;
T c = T(1);
if(weighted) cin >> c;
if(directed) add_directed_edge(a, b, c);
else add_edge(a, b, c);
}
}
inline vector< Edge< T > > &operator[](const int &k) {
return g[k];
}
inline const vector< Edge< T > > &operator[](const int &k) const {
return g[k];
}
};
template< typename T = int >
using Edges = vector< Edge< T > >;
#line 2 "structure/union-find/union-find.hpp"
struct UnionFind {
vector< int > data;
UnionFind() = default;
explicit UnionFind(size_t sz) : data(sz, -1) {}
bool unite(int x, int y) {
x = find(x), y = find(y);
if(x == y) return false;
if(data[x] > data[y]) swap(x, y);
data[x] += data[y];
data[y] = x;
return true;
}
int find(int k) {
if(data[k] < 0) return (k);
return data[k] = find(data[k]);
}
int size(int k) {
return -data[find(k)];
}
bool same(int x, int y) {
return find(x) == find(y);
}
vector< vector< int > > groups() {
int n = (int) data.size();
vector< vector< int > > ret(n);
for(int i = 0; i < n; i++) {
ret[find(i)].emplace_back(i);
}
ret.erase(remove_if(begin(ret), end(ret), [&](const vector< int > &v) {
return v.empty();
}), end(ret));
return ret;
}
};
#line 3 "graph/tree/offline-lca.hpp"
/**
* @brief Offline LCA(オフライン最小共通祖先)
**/
template< typename T >
vector< int > offline_lca(const Graph< T > &g, vector< pair< int, int > > &qs, int root = 0) {
int n = (int) g.size();
UnionFind uf(n);
vector< int > st(n), mark(n), ptr(n), ans(qs.size(), -1);
int top = 0;
st[top] = root;
for(auto&[l, r]: qs) mark[l]++, mark[r]++;
vector< vector< pair< int, int > > > q(n);
for(int i = 0; i < n; i++) {
q[i].reserve(mark[i]);
mark[i] = -1;
ptr[i] = (int) g[i].size();
}
for(int i = 0; i < qs.size(); i++) {
q[qs[i].first].emplace_back(qs[i].second, i);
q[qs[i].second].emplace_back(qs[i].first, i);
}
auto run = [&](int u) -> bool {
while(ptr[u]) {
int v = g[u][--ptr[u]];
if(mark[v] == -1) {
st[++top] = v;
return true;
}
}
return false;
};
while(~top) {
int u = st[top];
if(mark[u] == -1) {
mark[u] = u;
} else {
uf.unite(u, g[u][ptr[u]]);
mark[uf.find(u)] = u;
}
if(not run(u)) {
for(auto&[v, i]: q[u]) {
if(~mark[v] and ans[i] == -1) {
ans[i] = mark[uf.find(v)];
}
}
--top;
}
}
return ans;
}