Graph

Models relationships between things—social networks, maps, dependencies, etc.

class Graph {
  private adjacencyList: Map<string, string[]>;

  constructor() {
    this.adjacencyList = new Map();
  }

  // Add a vertex
  addVertex(vertex: string): void {
    if (!this.adjacencyList.has(vertex)) {
      this.adjacencyList.set(vertex, []);
    }
  }

  // Add an undirected edge
  addEdge(vertex1: string, vertex2: string): void {
    // Ensure vertices exist
    this.addVertex(vertex1);
    this.addVertex(vertex2);

    // Add edges (undirected)
    this.adjacencyList.get(vertex1)!.push(vertex2);
    this.adjacencyList.get(vertex2)!.push(vertex1);
  }

  // Check if an edge exists
  hasEdge(vertex1: string, vertex2: string): boolean {
    const neighbors = this.adjacencyList.get(vertex1);
    return neighbors ? neighbors.includes(vertex2) : false;
  }
}

const graph = new Graph();
graph.addVertex("A");
graph.addVertex("B");
graph.addEdge("A", "B");
console.log(graph.hasEdge("A", "B")); // Output: true
console.log(graph.hasEdge("A", "C")); // Output: false

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