1 files changed, 19 insertions, 0 deletions
diff --git a/graph/havelHakimi.cpp b/graph/havelHakimi.cpp
new file mode 100644
index 0000000..9fb9846
--- /dev/null
+++ b/graph/havelHakimi.cpp
@@ -0,0 +1,19 @@
+vector<vector<int>> havelHakimi(const vector<int>& deg) {
+	priority_queue<pair<int, int>> pq;
+	for (int i = 0; i < sz(deg); i++) pq.push({deg[i], i});
+	vector<vector<int>> adj;
+	while (!pq.empty()) {
+		auto v = pq.top(); pq.pop();
+		if (sz(pq) < v.first) return {}; //ERROR
+		vector<pair<int, int>> todo;
+		for (int i = 0; i < v.first; i++) {
+			auto u = pq.top(); pq.pop();
+			adj[v.second].push_back(u.second);
+			adj[u.second].push_back(v.second);
+			u.first--;
+			if (u.first > 0) todo.push_back(u);
+		}
+		for (auto e : todo) pq.push(e);
+	}
+	return adj;
+}