Create number-of-connected-components-in-an-undirected-graph.cpp

Author: kamyu104

C++/number-of-connected-components-in-an-undirected-graph.cpp

@@ -0,0 +1,45 @@
+// Time:  O(nlog*n) ~= O(n), n is the length of the positions
+// Space: O(n)
+
+class Solution {
+public:
+    int countComponents(int n, vector<pair<int, int>>& edges) {
+        UnionFind union_find(n);
+        for (const auto& e : edges) {
+            union_find.union_set(e.first, e.second);
+        }
+        return union_find.length();
+    }
+
+private:
+    class UnionFind {
+        public:
+            UnionFind(const int n) : set(n) {
+                iota(set.begin(), set.end(), 0);
+                count_ = n;
+            }
+
+            int find_set(int x) {
+               if (set[x] != x) {
+                   set[x] = find_set(set[x]);  // Path compression.
+               }
+               return set[x];
+            }
+
+            void union_set(const int x, const int y) {
+                int x_root = find_set(x), y_root = find_set(y);
+                if (x_root != y_root) {
+                    set[min(x_root, y_root)] = max(x_root, y_root);
+                    --count_;
+                }
+            }
+
+            int length() const {
+                return count_;
+            }
+
+        private:
+            vector<int> set;
+            int count_;
+    };
+};