1 files changed, 61 insertions, 0 deletions

diff --git a/04_graph_algorithms/high_score_1673.cpp b/04_graph_algorithms/high_score_1673.cpp
new file mode 100644
index 0000000..c327ba0
--- /dev/null
+++ b/04_graph_algorithms/high_score_1673.cpp
@@ -0,0 +1,61 @@
+#include <algorithm>
+#include <iostream>
+#include <tuple>
+#include <vector>
+
+constexpr long long inf = 999999999999999LL;
+
+size_t findcycle(
+        size_t v,
+        const std::vector<std::tuple<size_t, size_t, long long>>& a, 
+        const std::vector<size_t>& p
+) {
+        std::vector<bool> visited(p.size(), false);
+        visited[v] = true;
+        size_t u = p[v];
+        while (!visited[u]) {
+                visited[u] = true;
+                u = p[u];
+        }
+        return u;
+}
+
+int main() {
+        size_t n, m;
+        std::cin >> n >> m;
+        std::vector<std::tuple<size_t, size_t, long long>> a(m);
+        for (size_t i = 0; i < m; i++) {
+                size_t x, y;
+                long long w;
+                std::cin >> x >> y >> w;
+                a[i] = {x-1, y-1, w};
+        }
+
+        std::vector<size_t> p(n, n);
+        std::vector<long long> d(n, -inf);
+        d[0] = 0;
+        std::vector<bool> reach_1(n, false), reach_n(n, false);
+        reach_1[0] = reach_n[n-1] = true;
+        for (size_t i = 0; i < n; i++) {
+                for (auto [v, u, w] : a) {
+                        if (d[u] < d[v] + w) {
+                                d[u] = d[v] + w;
+                                p[u] = v;
+                        }
+                        reach_n[v] = reach_n[v] || reach_n[u];
+                        reach_1[u] = reach_1[u] || reach_1[v];
+                }
+        }
+
+        for (auto [v, u, w] : a) {
+                if (d[u] < d[v] + w) {
+                        size_t x = findcycle(u, a, p);
+                        if (reach_1[x] && reach_n[x]) {
+                                std::cout << "-1\n";
+                                return 0;
+                        }
+                }
+        }
+
+        std::cout << d[n-1] << "\n";
+}