fix: #86

src/data-structures/graph/directed-graph.ts

@@ -261,7 +261,8 @@ export class DirectedGraph<
     if (vertex) {
       const neighbors = this.getNeighbors(vertex);
       for (const neighbor of neighbors) {
-        this._inEdgeMap.delete(neighbor);
+        // this._inEdgeMap.delete(neighbor);
+        this.deleteEdgeSrcToDest(vertex, neighbor);
       }
       this._outEdgeMap.delete(vertex);
       this._inEdgeMap.delete(vertex);

test/unit/data-structures/graph/directed-graph.test.ts

@@ -995,3 +995,31 @@ describe('DirectedGraph tarjan', () => {
     expect(getAsVerticesArrays(sccs)).toEqual([['K', 'J', 'I', 'H', 'D', 'C', 'B'], ['G', 'F', 'E'], ['A']]);
   });
 });
+
+describe('delete', () => {
+  it(`deleteVertex deletes all of it's neighbors from the inEdge Map`, () => {
+
+    const graph = new DirectedGraph();
+    graph.addVertex('A');
+    graph.addVertex('B');
+    graph.addVertex('C');
+
+    graph.addEdge('B', 'A');
+    graph.addEdge('C', 'A');
+
+    // 'Incoming to A should contain ['B','C']
+    expect(graph.incomingEdgesOf('A').map((e) => e.src)).toEqual(['B','C']); //  ['B','C']
+
+    // Now delete B, which has no direct link to C, only that C -> A.
+    graph.deleteVertex('B');
+
+    // Now if we do the same call to incoming edges for we should get only ['C']
+    expect(graph.incomingEdgesOf('A').map((e) => e.src)).toEqual(['C']); // [];
+
+    // but it only shows an empty array, since we deleted all of `A's edges, not just the one to `B`.
+
+    // If we check C, it correctly shows A as an outgoing edge,
+    // even though A no longer has any knowledge of C linking to it.
+    expect(graph.outgoingEdgesOf('C').map((e) => e.dest)).toEqual(['A']);
+  });
+})