1 files changed, 54 insertions, 0 deletions

diff --git a/04_graph_algorithms/message_route_1667.cpp b/04_graph_algorithms/message_route_1667.cpp
new file mode 100644
index 0000000..280f7d6
--- /dev/null
+++ b/04_graph_algorithms/message_route_1667.cpp
@@ -0,0 +1,54 @@
+#include <iostream>
+#include <queue>
+#include <ranges>
+#include <vector>
+
+constexpr size_t inf = 1999999999;
+
+int main() {
+        size_t n, m;
+        std::cin >> n >> m;
+        std::vector<std::vector<size_t>> a(n);
+        for (size_t i = 0; i < m; i++) {
+                size_t x, y;
+                std::cin >> x >> y;
+                a[x-1].push_back(y-1);
+                a[y-1].push_back(x-1);
+        }
+
+        std::queue<size_t> q;
+        std::vector<size_t> d(n, inf);
+        d[0] = 0;
+        q.push(0);
+        while (!q.empty()) {
+                auto i = q.front();
+                q.pop();
+                if (i == n-1) break;
+                for (auto j : a[i]) {
+                        if (d[j] > d[i]+1) {
+                                d[j] = d[i] + 1;
+                                q.push(j);
+                        }
+                }
+        }
+
+        if (d[n-1] == inf) {
+                std::cout << "IMPOSSIBLE\n";
+        } else {
+                std::cout << d[n-1]+1 << "\n";
+                // Backtracking
+                std::vector<size_t> v;
+                v.push_back(n-1);
+                while (v.back() != 0) {
+                        for (auto j : a[v.back()]) {
+                                if (d[j] == d[v.back()]-1) {
+                                        v.push_back(j);
+                                        break;
+                                }
+                        }
+                }
+                for (auto x : v | std::views::reverse)
+                        std::cout << x+1 << " ";
+                std::cout << "\n";
+        }
+}