1 files changed, 44 insertions, 0 deletions

diff --git a/04_graph_algorithms/round_trip_1669.cpp b/04_graph_algorithms/round_trip_1669.cpp
new file mode 100644
index 0000000..c19b29d
--- /dev/null
+++ b/04_graph_algorithms/round_trip_1669.cpp
@@ -0,0 +1,44 @@
+#include <iostream>
+#include <vector>
+
+std::vector<int> cyc;
+
+int dfs(const std::vector<std::vector<int>>& a,
+    std::vector<bool>& v, int i, int p) {
+        v[i] = true;
+        for (auto x : a.at(i)) {
+                if (x == p) continue;
+                if (v.at(x)) {
+                        cyc.push_back(x);
+                        cyc.push_back(i);
+                        return x;
+                }
+                if (int r = dfs(a, v, x, i); r != 0) {
+                        cyc.push_back(i);
+                        if (r == i) {
+                                std::cout << cyc.size() << "\n";
+                                for (auto y : cyc) std::cout << y << " ";
+                                std::cout << "\n";
+                                exit(0);
+                        } else return r;
+                }
+        }
+        return 0;
+}
+
+int main() {
+        int n, m;
+        std::cin >> n >> m;
+        std::vector<std::vector<int>> a(n+1);
+        for (int i = 0; i < m; i++) {
+                int x, y;
+                std::cin >> x >> y;
+                a[x].push_back(y);
+                a[y].push_back(x);
+        }
+        std::vector<bool> v(n+1);
+        for (int i = 1; i <= n; i++)
+                if (!v.at(i))
+                        dfs(a, v, i, 0);
+        std::cout << "IMPOSSIBLE\n";
+}