Add Tarjan's algorithm.

Author: trekhleb

src/algorithms/graph/articulation-points/__test__/articulationPoints.test.js

@@ -55,6 +55,35 @@ describe('articulationPoints', () => {
     ]);
   });
 
+  it('should find articulation points in simple graph with back edge #2', () => {
+    const vertexA = new GraphVertex('A');
+    const vertexB = new GraphVertex('B');
+    const vertexC = new GraphVertex('C');
+    const vertexD = new GraphVertex('D');
+    const vertexE = new GraphVertex('E');
+
+    const edgeAB = new GraphEdge(vertexA, vertexB);
+    const edgeBC = new GraphEdge(vertexB, vertexC);
+    const edgeCD = new GraphEdge(vertexC, vertexD);
+    const edgeAE = new GraphEdge(vertexA, vertexE);
+    const edgeCE = new GraphEdge(vertexC, vertexE);
+
+    const graph = new Graph();
+
+    graph
+      .addEdge(edgeAB)
+      .addEdge(edgeAE)
+      .addEdge(edgeCE)
+      .addEdge(edgeBC)
+      .addEdge(edgeCD);
+
+    const articulationPointsSet = articulationPoints(graph);
+
+    expect(articulationPointsSet).toEqual([
+      vertexC,
+    ]);
+  });
+
   it('should find articulation points in graph', () => {
     const vertexA = new GraphVertex('A');
     const vertexB = new GraphVertex('B');

src/algorithms/graph/articulation-points/articulationPoints.js

@@ -14,7 +14,7 @@ class VisitMetadata {
 
     // We need this in order to check graph root node, whether it has two
     // disconnected children or not.
-    this.childrenCount = 0;
+    this.independantChildrenCount = 0;
   }
 }
 
@@ -57,7 +57,7 @@ export default function articulationPoints(graph) {
         visitedSet[previousVertex.getKey()].childVertex = currentVertex;
 
         // Update children counter for previous vertex.
-        visitedSet[previousVertex.getKey()].childrenCount += 1;
+        visitedSet[previousVertex.getKey()].independantChildrenCount += 1;
       }
     },
     /**
@@ -71,7 +71,7 @@ export default function articulationPoints(graph) {
       // 2. If its visited time is <= low time of adjacent vertex.
       if (currentVertex === startVertex) {
         // Check that it has at least two independent children.
-        if (visitedSet[currentVertex.getKey()].childrenCount >= 2) {
+        if (visitedSet[currentVertex.getKey()].independantChildrenCount >= 2) {
           articulationPointsSet.push(currentVertex);
         }
       } else {