Detecting cycles in a directed graph

cycle-finder.groovy

//#!/usr/bin/env groovy

/**
 * Finding cycles in a directed graph
 */
class CycleFinder {

    // Zbiór wierzchołków w grafie
    def V
    
    // Adj(v) - zbiór wierzchołków sąsiadujących z v
    def Adj
   
    def visited = [:]
    
    def cycles = []
    
    CycleFinder(V, Adj) {
        this.V   = V
        this.Adj = Adj
    }
    
    public findCycles() {
        dfs()
        return cycles
    }
    
    def dfs() {
        def path = new Stack()
        for(u in V) {
            if(!visited[u]) {
                dfsVisit(u, path)
            }
        }      
    }
    def dfsVisit(u, path) {
        visited[u] = true
        path.push(u)
        for(v in Adj(u)) {
            int i = path.indexOf(v)
            if(i != -1) {
                def cycle = new ArrayList(path[i..-1])
                cycles.add(cycle)
            }        
            if(!visited[v]) {
                dfsVisit(v, path)
            }
        }
        path.pop()
    }

}