Graph Code Challenges

javascript/code-challenges/graphs/README.md

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+# Graphs
+<!-- Short summary or background information -->
+
+## Challenge
+Implement your own Graph. The graph should be represented as an adjacency list.
+The Graph class should have the following methods: `addVertex`, `addEdge`, `getVertices`,
+`getNeighbors`, `getSize`
+
+## Approach & Efficiency
+| Method  | Time Complexity |
+| ---- | ---- |
+| `addVertex` | O(1) |
+| `addEdge` | O(1) |
+| `getVertices` | O(n) |
+| `getNeighbors` | O(n) |
+| `getSize` | O(n)|
+
+## Methods
+
+`addVertex`
+
+- Adds a new vertex to the graph and returns the added vertex.
+
+`addEdge`
+
+- Adds an edge between two vertices and returns nothing.
+
+`getVertices`
+
+- Returns all the vertices in the graph.
+
+`getNeighbors`
+
+- Returns all the vertices connected to a give vertex.
+
+`getSize`
+
+- Returns the total number of vertices in the graph
+
+### Run Solution
+
+```sh
+# Install dependencies
+npm install
+
+# run jest tests for undirected-graph.js
+npm test undirected-graph.test.js
+```
+### Sources
+
+[Spread Syntax](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax)
+
+[JavaScript Algorithms and Data Structures Masterclass - Colt Steele](https://www.udemy.com/course/js-algorithms-and-data-structures-masterclass/)
+

javascript/code-challenges/graphs/undirected-graph.js

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+class UndirectedGraph {
+  constructor(){
+      this.adjacencyList = {}
+  }
+  addVertex(vertex) {
+      if(!this.adjacencyList[vertex]) {
+          this.adjacencyList[vertex] = []
+          return vertex
+      }
+  }
+  removeVertex(vertex) {
+      while(this.adjacencyList[vertex].length){
+          const adjacentVertex = this.adjacencyList[vertex].pop()
+          this.removeEdge(vertex, adjacentVertex)
+      }
+
+      delete this.adjacencyList[vertex]
+  }
+  addEdge(vertex1, vertex2) {
+      // Push values
+      this.adjacencyList[vertex1].push(vertex2)
+      this.adjacencyList[vertex2].push(vertex1)
+      // Remove duplicates
+      this.adjacencyList[vertex1] = [...new Set(this.adjacencyList[vertex1])]
+      this.adjacencyList[vertex2] = [...new Set(this.adjacencyList[vertex2])]
+  }
+  removeEdge(vertex1, vertex2) {
+      this.adjacencyList[vertex1] = this.adjacencyList[vertex1].filter(
+          edge => edge !== vertex2
+      )
+      this.adjacencyList[vertex2] = this.adjacencyList[vertex2].filter(
+          edge => edge !== vertex1
+      )
+  }
+  getVertices() {
+      return Object.keys(this.adjacencyList)
+  }
+  getNeighbors(vertex) {
+      return this.adjacencyList[vertex]
+  }
+  getSize() {
+      return Object.keys(this.adjacencyList).length
+  }
+}
+
+module.exports = UndirectedGraph

javascript/code-challenges/graphs/undirected-graph.test.js

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+const { describe, it } = require('eslint/lib/rule-tester/rule-tester')
+const UndirectedGraph = require('./undirected-graph')
+
+let testGraph
+
+
+describe('Given Graphs', () => {
+  describe('When happy path',  () => {
+    beforeEach(() => {
+      testGraph = new UndirectedGraph()
+
+      // Add vertices before adding edge
+      testGraph.addVertex('Seattle')
+      testGraph.addVertex('Tokyo')
+    })
+
+    it('Vertex can be successfully added to the graph', () => {
+      testGraph.addVertex('NYC')
+      expect(testGraph.adjacencyList['NYC']).toEqual([])
+      expect(testGraph.adjacencyList['Seattle']).toEqual([])
+      expect(testGraph.adjacencyList['Tokyo']).toEqual([])
+    })
+
+    it('An edge can be successfully added to the graph', () => {
+      testGraph.addEdge('Seattle', 'Tokyo')
+      expect(testGraph.adjacencyList['Seattle']).toEqual(['Tokyo'])
+      expect(testGraph.adjacencyList['Tokyo']).toEqual(['Seattle'])
+    })
+
+    it('A collection of all vertices can be properly retrieved from the graph', () => {
+      expect(testGraph.getVertices() === ['Seattle', 'Tokyo'])
+    })
+
+    it('All appropriate neighbors can be retrieved from the graph', () => {
+      testGraph.addEdge('Seattle', 'Tokyo')  
+      expect(testGraph.getNeighbors('Seattle')).toEqual(['Tokyo'])
+      expect(testGraph.getNeighbors('Tokyo')).toEqual(['Seattle'])
+    })
+
+    // TODO handle weighted edges
+    it.todo('Neighbors are returned with the weight between vertices included')
+
+    it('The proper size is returned, representing the number of vertices in the graph', () => {
+      expect(testGraph.getSize()).toEqual(2)
+    })
+  })
+
+  describe('When edge case', () => {
+    it('A graph with only one vertex and edge can be properly returned', () => {
+      // How would a graph with one vertex have an edge?
+      let testGraph = new UndirectedGraph()
+      testGraph.addVertex('Seattle')
+      expect(testGraph.getVertices()).toEqual(['Seattle'])
+    })
+
+    it('An empty graph properly returns size', () => {
+      let testGraph = new UndirectedGraph()
+      expect(testGraph.getSize()).toEqual(0)
+    })
+  })
+})