Use Infinity instead of zero in Graph adjacency matrix to show that vertices are not connected.

Muhammad Usman · Muhammad Usman · commit a08b8427c457 · 2018-05-22T07:10:46.000+03:00
diff --git a/src/algorithms/graph/hamiltonian-cycle/hamiltonianCycle.js b/src/algorithms/graph/hamiltonian-cycle/hamiltonianCycle.js
@@ -15,7 +15,7 @@ function isSafe(adjacencyMatrix, verticesIndices, cycle, vertexCandidate) {
   const endVertexAdjacencyIndex = verticesIndices[endVertex.getKey()];
 
   // Check if last vertex in the path and candidate vertex are adjacent.
-  if (!adjacencyMatrix[endVertexAdjacencyIndex][candidateVertexAdjacencyIndex]) {
+  if (adjacencyMatrix[endVertexAdjacencyIndex][candidateVertexAdjacencyIndex] === Infinity) {
     return false;
   }
 
@@ -43,7 +43,7 @@ function isCycle(adjacencyMatrix, verticesIndices, cycle) {
   const endVertexAdjacencyIndex = verticesIndices[endVertex.getKey()];
 
   // Check if we can go from end vertex to the start one.
-  return !!adjacencyMatrix[endVertexAdjacencyIndex][startVertexAdjacencyIndex];
+  return adjacencyMatrix[endVertexAdjacencyIndex][startVertexAdjacencyIndex] !== Infinity;
 }
 
 /**
diff --git a/src/data-structures/graph/Graph.js b/src/data-structures/graph/Graph.js
@@ -177,18 +177,17 @@ export default class Graph {
     const vertices = this.getAllVertices();
     const verticesIndices = this.getVerticesIndices();
 
-    // Init matrix with zeros.
+    // Init matrix with infinities meaning that there is no ways of
+    // getting from one vertex to another yet.
     const adjacencyMatrix = Array(vertices.length).fill(null).map(() => {
-      return Array(vertices.length).fill(0);
+      return Array(vertices.length).fill(Infinity);
     });
 
     // Fill the columns.
     vertices.forEach((vertex, vertexIndex) => {
       vertex.getNeighbors().forEach((neighbor) => {
         const neighborIndex = verticesIndices[neighbor.getKey()];
-        adjacencyMatrix[vertexIndex][neighborIndex] = this.isDirected ?
-          this.findEdge(vertex, neighbor).weight :
-          1;
+        adjacencyMatrix[vertexIndex][neighborIndex] = this.findEdge(vertex, neighbor).weight;
       });
     });
 
diff --git a/src/data-structures/graph/__test__/Graph.test.js b/src/data-structures/graph/__test__/Graph.test.js
@@ -348,10 +348,10 @@ describe('Graph', () => {
 
     const adjacencyMatrix = graph.getAdjacencyMatrix();
     expect(adjacencyMatrix).toEqual([
-      [0, 1, 0, 0],
-      [1, 0, 1, 1],
-      [0, 1, 0, 1],
-      [0, 1, 1, 0],
+      [Infinity, 0, Infinity, Infinity],
+      [0, Infinity, 0, 0],
+      [Infinity, 0, Infinity, 0],
+      [Infinity, 0, 0, Infinity],
     ]);
   });
 
@@ -375,10 +375,10 @@ describe('Graph', () => {
 
     const adjacencyMatrix = graph.getAdjacencyMatrix();
     expect(adjacencyMatrix).toEqual([
-      [0, 2, 0, 0],
-      [0, 0, 1, 7],
-      [0, 0, 0, 5],
-      [0, 0, 0, 0],
+      [Infinity, 2, Infinity, Infinity],
+      [Infinity, Infinity, 1, 7],
+      [Infinity, Infinity, Infinity, 5],
+      [Infinity, Infinity, Infinity, Infinity],
     ]);
   });
 });

Original file line number	Diff line number	Diff line change
`@@ -15,7 +15,7 @@ function isSafe(adjacencyMatrix, verticesIndices, cycle, vertexCandidate) {`
`15`	`15`	`const endVertexAdjacencyIndex = verticesIndices[endVertex.getKey()];`
`16`	`16`
`17`	`17`	`// Check if last vertex in the path and candidate vertex are adjacent.`
`18`		`- if (!adjacencyMatrix[endVertexAdjacencyIndex][candidateVertexAdjacencyIndex]) {`
	`18`	`+ if (adjacencyMatrix[endVertexAdjacencyIndex][candidateVertexAdjacencyIndex] === Infinity) {`
`19`	`19`	`return false;`
`20`	`20`	`}`
`21`	`21`
`@@ -43,7 +43,7 @@ function isCycle(adjacencyMatrix, verticesIndices, cycle) {`
`43`	`43`	`const endVertexAdjacencyIndex = verticesIndices[endVertex.getKey()];`
`44`	`44`
`45`	`45`	`// Check if we can go from end vertex to the start one.`
`46`		`- return !!adjacencyMatrix[endVertexAdjacencyIndex][startVertexAdjacencyIndex];`
	`46`	`+ return adjacencyMatrix[endVertexAdjacencyIndex][startVertexAdjacencyIndex] !== Infinity;`
`47`	`47`	`}`
`48`	`48`
`49`	`49`	`/**`