[cses] Add C++ solution for 1666 - Building Roads

Author: abeaumont

cses/1666-1.ans

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+1
+1 3

cses/1666-1.in

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+4 2
+1 2
+3 4

cses/1666.cc

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+// https://cses.fi/problemset/task/1666
+#include <bits/stdc++.h>
+
+using namespace std;
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+
+vi s;
+vvi g;
+int n;
+
+void dfs(int u) {
+  s[u] = 1;
+  for (int v : g[u])
+    if (!s[v])
+      dfs(v);
+}
+
+int main() {
+  int m, u, v;
+  cin >> n >> m;
+  g = vvi(n);
+  for (int i = 0; i < m; i++) {
+    cin >> u >> v;
+    u--; v--;
+    g[u].push_back(v);
+    g[v].push_back(u);
+  }
+  s = vi(n);
+  vi b;
+  dfs(0);
+  for (int i = 1; i < n; i++)
+    if (!s[i]) {
+      b.push_back(i);
+      dfs(i);
+    }
+  cout << b.size() << endl;
+  for (int x : b)
+    cout << 1 << " " << x + 1 << endl;
+}