Fix TransitiveReduction not to wrongly report cycles (#84)

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),  and this project
 adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.16.1] - 2023-03-06
+
+### Fixed
+* Fixed `TransitiveReduction` not to incorrectly report cycles.
+
 ## [0.16.0] - 2023-03-01
 
 **This release contains breaking changes of the public API (see "Changed").**

dag.go

@@ -114,6 +114,7 @@ func TransitiveReduction[K comparable, T any](g Graph[K, T]) (Graph[K, T], error
 
 				visited[current] = struct{}{}
 				onStack[current] = true
+				stack = append(stack, current)
 
 				// Also, if the vertex is a leaf node, remove it from the stack.
 				if len(adjacencyMap[current]) == 0 {

dag_test.go

@@ -130,6 +130,31 @@ func TestDirectedTransitiveReduction(t *testing.T) {
 			},
 			shouldFail: true,
 		},
+		"graph from issue 83": {
+			vertices: []string{"_root", "A", "B", "C", "D", "E", "F"},
+			edges: []Edge[string]{
+				{Source: "_root", Target: "A"},
+				{Source: "_root", Target: "B"},
+				{Source: "_root", Target: "C"},
+				{Source: "_root", Target: "D"},
+				{Source: "_root", Target: "E"},
+				{Source: "_root", Target: "F"},
+				{Source: "E", Target: "C"},
+				{Source: "F", Target: "D"},
+				{Source: "F", Target: "C"},
+				{Source: "F", Target: "E"},
+				{Source: "C", Target: "A"},
+				{Source: "C", Target: "B"},
+			},
+			expectedEdges: []Edge[string]{
+				{Source: "_root", Target: "F"},
+				{Source: "F", Target: "D"},
+				{Source: "F", Target: "E"},
+				{Source: "E", Target: "C"},
+				{Source: "C", Target: "A"},
+				{Source: "C", Target: "B"},
+			},
+		},
 	}
 
 	for name, test := range tests {