From 177f34300f8ef57797deb0acb03c1fd8a9ee87b5 Mon Sep 17 00:00:00 2001
From: Edson Neto <72220739+emn2@users.noreply.github.com>
Date: Tue, 5 Oct 2021 08:09:05 -0300
Subject: [PATCH] Algorithm to find negative cycles in a graph

---
 Graphs/negativeCycleFinding.cpp | 43 +++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 Graphs/negativeCycleFinding.cpp

diff --git a/Graphs/negativeCycleFinding.cpp b/Graphs/negativeCycleFinding.cpp
new file mode 100644
index 0000000..0f062c8
--- /dev/null
+++ b/Graphs/negativeCycleFinding.cpp
@@ -0,0 +1,43 @@
+struct Edge {
+    ll a, b, cost;
+};
+
+int n, m;
+vector<Edge> edges;
+const ll INF = 1e9 + 5;
+
+void solve(){
+    vector<ll> d(n);
+    vector<int> p(n, -1);
+    int x;
+    for (int i = 0; i < n; ++i) {
+        x = -1;
+        for (Edge e : edges) {
+            if (d[e.a] + e.cost < d[e.b]) {
+                d[e.b] = d[e.a] + e.cost;
+                p[e.b] = e.a;
+                x = e.b;
+            }
+        }
+    }
+
+    if (x == -1) {
+        cout << "NO\n";
+    } else {
+        for (int i = 0; i < n; ++i)
+            x = p[x];
+
+        vector<int> cycle;
+        for (int v = x;; v = p[v]) {
+            cycle.push_back(v);
+            if (v == x && cycle.size() > 1)
+                break;
+        }
+        reverse(cycle.begin(), cycle.end());
+
+        cout << "YES\n";
+        for (int v : cycle)
+            cout << v+1 << ' ';
+        cout << endl;
+    }
+}