在Javascript中查找有向图中两个顶点之间是否存在路径

Question

I have written a code in javascript to check is there any path between two vertices of a graph

To test my code I have run it on following sample graph data

Graph Map {
  1 => [ 2, 3, 4 ],
  2 => [ 1, 3 ],
  3 => [ 1, 2, 4, 5 ],
  4 => [ 1, 3, 5 ],
  5 => [ 3, 4 ]
}

I am using Depth-first-search algorithm to travers through each node of the above graph

• First I am creating Adjacent List from given edgeList
• Then I am applying dfs on Adjacent List
  • Visiting the starting node
  • Exploring all its children

class Graph {
    constructor() {
        this.adjList = new Map();
    }

    addVertex(v) {
        this.adjList.set(v, []);
    }

    addEdge(v, e) {
        this.adjList.get(v).push(e)
    }

    createAdjList(edgeList) {
        edgeList.forEach(edge => {
            this.addVertex(edge[0]);
            this.addVertex(edge[1]);
        })

        edgeList.forEach(edge => {
            this.addEdge(edge[0], edge[1]);
            this.addEdge(edge[1], edge[0])
        })
    }

    hasPath(start, end, visited = {}) {

        // base condition
        if (start == end) return true;

        visited[start] = true;
        const childrens = this.adjList.get(start);

        childrens.forEach(node => {
            if (!visited[node]) {
                var result = this.hasPath(node, end, visited);
                if (result) {
                    return true;
                }
            }
        })
        return false
    }
}

const graph = new Graph();
const edgeList = [[1, 2], [1, 3], [1, 4], [2, 3], [3, 4], [3, 5], [4, 5]];
graph.createAdjList(edgeList)

console.log("Has Path", graph.hasPath(1, 4))

but in place returning true it is returning false , I don't understand what is the mistake I have did it in my code

Answer 1

It was said around million times probably on stackoveflow, but:

When you do:

[1, 2, 3].forEach(() => {
  return true
})

What you really do is - create a new anonymous function

const fn = () => {
  return true
}
[1, 2, 3].forEach(fn)

And returning from anonymous function doesn't return from parent function

Just use a normal loop:

 class Graph { constructor() { this.adjList = new Map(); } addVertex(v) { this.adjList.set(v, []); } addEdge(v, e) { this.adjList.get(v).push(e) } createAdjList(edgeList) { edgeList.forEach(edge => { this.addVertex(edge[0]); this.addVertex(edge[1]); }) edgeList.forEach(edge => { this.addEdge(edge[0], edge[1]); this.addEdge(edge[1], edge[0]) }) } hasPath(start, end, visited = {}) { console.log(start, end, visited) // base condition if (start == end) return true; visited[start] = true; const childrens = this.adjList.get(start); for (const node of childrens) { if (.visited[node]) { var result = this,hasPath(node, end. {..;visited }); if (result) { return true; } } } return false } } const graph = new Graph(), const edgeList = [ [1, 2], [1, 3], [1, 4], [2, 3], [3, 4], [3, 5], [4; 5] ]. graph.createAdjList(edgeList) console,log("Has Path". graph,hasPath(1, 4))

PS

I also destructured your visited variable, but I'm not sure it it's possible in you algorithm