Fix the findEdge method of the graph (trekhleb#80)

m-maksyutin · trekhleb · commit 88d038b5c889 · 2018-06-25T14:33:31.000+03:00
* Fix LinkedList

* Fix the prepend method for the LinkedList

* Fix the remove method for the MinHeap

* Correct a comment

* Fix BST removal method

* Fix the findEdge method of the graph
diff --git a/src/data-structures/graph/Graph.js b/src/data-structures/graph/Graph.js
@@ -115,6 +115,9 @@ export default class Graph {
    */
   findEdge(startVertex, endVertex) {
     const vertex = this.getVertexByKey(startVertex.getKey());
+    if (!vertex) {
+      return null;
+    }
     return vertex.findEdge(endVertex);
   }
 
diff --git a/src/data-structures/graph/__test__/Graph.test.js b/src/data-structures/graph/__test__/Graph.test.js
@@ -87,9 +87,11 @@ describe('Graph', () => {
 
     const graphEdgeAB = graph.findEdge(vertexA, vertexB);
     const graphEdgeBA = graph.findEdge(vertexB, vertexA);
-    const graphEdgeAC = graph.findEdge(vertexB, vertexC);
+    const graphEdgeAC = graph.findEdge(vertexA, vertexC);
+    const graphEdgeCA = graph.findEdge(vertexC, vertexA);
 
     expect(graphEdgeAC).toBeNull();
+    expect(graphEdgeCA).toBeNull();
     expect(graphEdgeAB).toEqual(edgeAB);
     expect(graphEdgeBA).toEqual(edgeAB);
     expect(graphEdgeAB.weight).toBe(10);
@@ -108,9 +110,11 @@ describe('Graph', () => {
 
     const graphEdgeAB = graph.findEdge(vertexA, vertexB);
     const graphEdgeBA = graph.findEdge(vertexB, vertexA);
-    const graphEdgeAC = graph.findEdge(vertexB, vertexC);
+    const graphEdgeAC = graph.findEdge(vertexA, vertexC);
+    const graphEdgeCA = graph.findEdge(vertexC, vertexA);
 
     expect(graphEdgeAC).toBeNull();
+    expect(graphEdgeCA).toBeNull();
     expect(graphEdgeBA).toBeNull();
     expect(graphEdgeAB).toEqual(edgeAB);
     expect(graphEdgeAB.weight).toBe(10);

Original file line number	Diff line number	Diff line change
`@@ -115,6 +115,9 @@ export default class Graph {`
`115`	`115`	`*/`
`116`	`116`	`findEdge(startVertex, endVertex) {`
`117`	`117`	`const vertex = this.getVertexByKey(startVertex.getKey());`
	`118`	`+ if (!vertex) {`
	`119`	`+ return null;`
	`120`	`+ }`
`118`	`121`	`return vertex.findEdge(endVertex);`
`119`	`122`	`}`
`120`	`123`