data-structures-again/src/graph/dfs.js

A Javascript library of simple data structures

class DepthFirstPath {
    constructor(graph, startVertex, useRecursiveApproach = true) {
        this.visited = new Set()
        this.edgeTo = new Map()

        if (useRecursiveApproach) {
            this._dfs(graph, startVertex)
        } else this._dfsNonRecursive(graph, startVertex)
    }

    _dfs(graph, vertex) {
        graph.adjTo(vertex).forEach(v => {
            if (this.visited.has(v)) return
            this.visited.add(v)
            this.edgeTo.set(v, vertex)
            this._dfs(graph, v)
        })
    }

    _dfsNonRecursive(graph, vertex) {
        const stack = [[vertex]]

        let parentNode = null
        while (stack.length > 0) {
            const neighbors = stack[stack.length - 1]
            if (neighbors.length === 0) {
                stack.pop()
                continue
            }

            const neighbor = neighbors.pop()

            if (this.visited.has(neighbor)) continue

            this.visited.add(neighbor)
            this.edgeTo.set(neighbor, parentNode)
            parentNode = neighbor
            stack.push(
                graph
                    .adjTo(neighbor)
                    .filter(v => !this.visited.has(v))
                    .reverse()
            )
        }
    }

    hasPathTo(vertex) {
        return this.visited.has(vertex)
    }

    pathTo(vertex) {
        if (!this.hasPathTo(vertex)) return []

        const path = []
        let cur = vertex

        while (cur) {
            path.push(cur)
            cur = this.edgeTo.get(cur)
        }

        return path.reverse()
    }
}

module.exports = DepthFirstPath