Create connecting-cities-with-minimum-cost.cpp

C++/connecting-cities-with-minimum-cost.cpp

@@ -0,0 +1,53 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    int minimumCost(int N, vector<vector<int>>& connections) {
+        sort(connections.begin(), connections.end(),
+             [](const auto& a, const auto& b) {
+                return a[2] < b[2]; 
+             });
+        UnionFind union_find(N);
+        int result = 0;
+        for (const auto& c : connections) {
+            if (union_find.union_set(c[0] - 1, c[1] - 1)) {
+                result += c[2];
+            }
+        }
+        return union_find.size() == 1 ? result : -1;
+    }
+
+private:
+    class UnionFind {
+    public:
+        UnionFind(const int n) : set_(n), count_(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);
+            --count_;
+            return true;
+        }
+
+        int size() const {
+            return count_;
+        }
+
+    private:
+        vector<int> set_;
+        int count_;
+    };
+};