vector<int> findMinHeightTrees(int n, vector<pair<int, int>>& edges) {
// Init
VI ans;
VVI adj(n);
QI q;
VI d(n, -1), pathTo(n);
for(auto& pr: edges) {
int u = pr.first, v = pr.second;
adj[u].push_back(v);
adj[v].push_back(u);
}
// Find one endpoint of longest path
int start = 0;
q.push(0);
d[0] = 0;
while(!q.empty()) {
int u = q.front(); q.pop();
start = u;
for(int v: adj[u]) {
if(d[v] == -1) {
d[v] = d[u] + 1;
q.push(v);
}
}
}
// Find longest path
int maxd = 0, end = start;
q = QI();
fill(d.begin(), d.end(), -1);
q.push(start);
d[start] = 0;
while(!q.empty()) {
int u = q.front(); q.pop();
maxd = d[u];
end = u;
for(int v: adj[u]) {
if(d[v] == -1) {
pathTo[v] = u;
d[v] = d[u] + 1;
q.push(v);
}
}
}
// Find mid points
int s = end;
for(int i = 0; i < maxd / 2; i++) {
s = pathTo[s];
}
ans.push_back(s);
if(maxd & 1) {
ans.push_back(pathTo[s]);
}
return ans;
}
bool Graph::isReachable(int src, int dest) {
if(src == dest)
return true;
bool visit[V];
fill(visit, visit+V, false);
QI q;
q.push(src);
LI::iterator iter;
visit[src] = true;
while(!q.empty()) {
int u = q.front();
q.pop();
iter = adj[u].begin();
for(; iter != adj[u].end(); iter++) {
if(*iter == dest)
return true;
if(!visit[*iter]) {
visit[*iter] = 1;
q.push(*iter);
}
}
}
return false;
}