void connect(int a, int b) {
if (a < 1 || a >= mParentId.size() || b < 1 || b >= mParentId.size()){
return;//error
}
auto aId = UnionFind(a);
auto bId = UnionFind(b);
if(aId != bId) {
mParentId[aId].first = bId;
mParentId[bId].second += mParentId[aId].second;
}
}
int query(int a) {
if (a < 1 || a >= mParentId.size()){
return -1;//error
}
auto aId = UnionFind(a);
return mParentId[aId].second;
}
vector<Edge> kruskal(int V, vector<Edge>& edges){
auto union_find = UnionFind(V);
sort(edges.begin(), edges.end());
vector<Edge> res;
for(auto& edge: edges){
if(union_find.unite(edge.from, edge.to)){
res.push_back(edge);
}
}
return res;
}
vector<int> numIslands2(int m, int n, vector<pair<int, int>>& positions) {
if(positions.empty()) return vector<int>();
UnionFind uf = UnionFind();
vector<int> res;
for(int i = 0; i < positions.size(); ++i){
int x = positions[i].first;
int y = positions[i].second;
int idx = x*n+y;
uf.add(idx);
if(x+1<m) uf.unionF(idx, (x+1)*n+y);
if(x>0) uf.unionF(idx, (x-1)*n+y);
if(y+1<n) uf.unionF(idx, x*n+y+1);
if(y>0) uf.unionF(idx, x*n+y-1);
res.push_back(uf.getCnt());
}
return res;
}
