Create minimize-malware-spread-ii.cpp

Author: kamyu104

C++/minimize-malware-spread-ii.cpp

@@ -0,0 +1,83 @@
+// Time:  O(n^3)
+// Space: O(n)
+
+class Solution {
+public:
+    int minMalwareSpread(vector<vector<int>>& graph, vector<int>& initial) {
+        unordered_set<int> initial_set(initial.cbegin(), initial.cend());
+        UnionFind union_find(graph.size());
+        for (int i = 0; i < graph.size(); ++i) {
+            if (initial_set.count(i)) {
+                continue;
+            }
+            for (int j = i + 1; j < graph.size(); ++j) {
+                if (initial_set.count(j)) {
+                    continue;
+                }
+                if (graph[i][j] == 1) {
+                    union_find.union_set(i, j);
+                }
+            }
+        }
+        unordered_map<int, int> union_size;
+        for (int i = 0; i < graph.size(); ++i) {
+            ++union_size[union_find.find_set(i)];
+        }
+        int result = numeric_limits<int>::max();
+        int total = numeric_limits<int>::max();
+        for (const auto& remove: initial) {
+            unordered_set<int> lookup;
+            int curr = 0;
+            for (const auto& i: initial) {
+                if (i == remove) {
+                    continue;
+                }
+                for (int j = 0; j < graph.size(); ++j) {
+                    if (initial_set.count(j)) {
+                        continue;
+                    }
+                    if (graph[i][j] == 1) {
+                        auto x = union_find.find_set(j);
+                        if (!lookup.count(x)) {
+                            curr += union_size[x];
+                            lookup.emplace(x);
+                        }
+                    }
+                }
+            }
+            if (curr < total ||
+                (curr == total && remove < result)) {
+                total = curr;
+                result = remove;
+            }
+        }
+        return result;
+    }
+
+private:
+    class UnionFind {
+        public:
+            UnionFind(const int n) : set_(n) {
+                iota(set_.begin(), set_.end(), 0);
+            }
+
+            int find_set(const int x) {
+               if (set_[x] != x) {
+                   set_[x] = find_set(set_[x]);  // Path compression.
+               }
+               return set_[x];
+            }
+
+            bool union_set(const int x, const int y) {
+                int x_root = find_set(x), y_root = find_set(y);
+                if (x_root == y_root) {
+                    return false;
+                }
+                set_[min(x_root, y_root)] = max(x_root, y_root);
+                return true;
+            }
+
+        private:
+            vector<int> set_;
+    };
+};