Cycle Detection

**** CYCLE DETECTION IN DIRECTED GRAPH ****

void dfs (int v) {
    visited[v] = 1;

    for every vertex that is reachable from v do
        if visited[vertex] = 0
            dfs (vertex)
        else if visited[vertex] = 1
            cycle = 1

    visited[v] = 2
}

---------------------------------------------

**** RECOVER THE DFS PATH IN GRAPH ****
dfs (int v) {
    visited[v] = 1;

    for every vertex that is reachable from v :
        if visited[vertex] = 0 :
            parent[vertex] = v
            dfs (vertex)
}

recover ( v ) {
    while parent[v] != -1 :
        print ( v )
        v = parent[v]
}
---------------------------------------------

**** CYCLE DETECTION IN UNDIRECTED GRAPH ****

dfs ( v , parent = -1 ) {
    visited[v] = 1

    for every vertex that is reachable from v :
        if vertex == parent : go to next vertex
        else if visited[vertex] == 0 :
                array_parent[vertex] = v
                dfs ( vertex, v )
        else if visited[vertex] == 1 :
            cycle = 1
            cycle_begin = vertex
            cycle_end = v

    visited[v] = 2
}

recover () {
    if cycle == 1 :
        answer = []

        while (cycle_end != cycle_begin) :
            answer.append (cycle_end)
            cycle_end = array_parent[cycle_end]

        print (answer)
}