Create 3607. Power Grid Maintenance (#928)

Author: Chayandas07

3607. Power Grid Maintenance

@@ -0,0 +1,51 @@
+class Solution {
+public:
+    struct DSU {
+        vector<int> p, sz;
+        DSU(int n=0): p(n+1), sz(n+1,1){
+            iota(p.begin(), p.end(), 0);
+        }
+        int find(int x){ return p[x]==x? x : p[x]=find(p[x]); }
+        void unite(int a, int b){
+            a = find(a); b = find(b);
+            if(a==b) return;
+            if(sz[a] < sz[b]) swap(a,b);
+            p[b]=a; sz[a]+=sz[b];
+        }
+    };
+
+    vector<int> processQueries(int c, vector<vector<int>>& connections, vector<vector<int>>& queries) {
+        DSU dsu(c);
+        for (auto &e : connections) dsu.unite(e[0], e[1]);
+
+        unordered_map<int, priority_queue<int, vector<int>, greater<int>>> heap;
+        heap.reserve(c*2);
+
+        for (int i = 1; i <= c; ++i) {
+            int r = dsu.find(i);
+            heap[r].push(i);
+        }
+
+        vector<char> offline(c+1, false);
+        vector<int> ans;
+        ans.reserve(queries.size());
+
+        for (auto &q : queries) {
+            int t = q[0], x = q[1];
+            if (t == 2) {
+                offline[x] = true;
+            } else {
+                if (!offline[x]) {
+                    ans.push_back(x);
+                } else {
+                    int r = dsu.find(x);
+                    auto &pq = heap[r];
+                    while (!pq.empty() && offline[pq.top()]) pq.pop();
+                    if (pq.empty()) ans.push_back(-1);
+                    else ans.push_back(pq.top());
+                }
+            }
+        }
+        return ans;
+    }
+};