Ejemplo n.º 1
0
def number_of_descendants(S, root):
    nd = {}
    for node in S:
        nd[node] = 0
    
    ancestors = create_ancestors(S, root)
    for node in nd:
        for a in ancestors:
            if node in ancestors[a]:
                nd[node] += 1
    return nd
Ejemplo n.º 2
0
def bridge_edges(G, root):
    S = create_rooted_spanning_tree(G, root)
    po = post_order(S, root)
    ancestors = create_ancestors(S, root)
    nd = number_of_descendants(S, root)
    l, h = po_low_high(S, root, po)

    bridges = []
    for node in S:
        for n in S[node]:
            if n not in ancestors[node]:
                if S[node][n] == 'green':
                    if h[n] <= po[n]:
                        if l[n] > abs(nd[n] - po[n]):
                            bridges.append((node, n))
    return bridges
Ejemplo n.º 3
0
def bridge_edges(G, root):
    S = create_rooted_spanning_tree(G, root)
    po = post_order(S, root)
    ancestors = create_ancestors(S, root)
    nd = number_of_descendants(S, root)
    l, h = po_low_high(S, root, po)

    bridges = []
    for node in S:
        for n in S[node]:
            if n not in ancestors[node]:
                if S[node][n] == 'green':
                    if h[n] <= po[n]:
                        if l[n] > abs(nd[n]-po[n]):
                            bridges.append((node, n))
    return bridges
Ejemplo n.º 4
0
def po_low_high(S, root, po):
    lpo, hpo = {}, {}
    ancestors = create_ancestors(S, root)
    reverse_po = dict(zip(po.values(), po))

    for i in range(1, len(reverse_po) + 1):
        n = reverse_po[i]
        temp = [po[n]]

        for node in S[n]:
            if node not in ancestors[n]:
                temp.append(po[node])
                for x in S[node]:
                    if S[node][x] == 'red':
                        temp.append(po[x])
        lpo[n], hpo[n] = min(temp), max(temp)

    return lpo, hpo
Ejemplo n.º 5
0
def po_low_high(S, root, po):
    lpo, hpo = {}, {}
    ancestors = create_ancestors(S, root)
    reverse_po = dict(zip(po.values(),po))

    for i in range(1, len(reverse_po)+1):
        n = reverse_po[i]
        temp = [po[n]]
        
        for node in S[n]:
            if node not in ancestors[n]:
                temp.append(po[node])
                for x in S[node]:
                    if S[node][x] == 'red':
                        temp.append(po[x])
        lpo[n], hpo[n] = min(temp), max(temp)
        
    return lpo, hpo