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executable file
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""" classes and functions for binary trees
"""
from myQueue.PrioQueue import PrioQueue
from Graph import *
inf = float("inf") # infinity
# Find nearest pathes from a single vertex to other reachable
# vertices using Dijkstra algorithm, with priority queue.
def dijkstra_shortest_paths(graph, v0):
vnum = graph.vertex_num()
assert 0 <= v0 < vnum
pathes = [None]*vnum
count = 0
cands = PrioQueue([(0, v0, v0)]) # 初始队列
while count < vnum and not cands.is_empty():
print(cands)
plen, u, vmin = cands.dequeue() # 取路径最短顶点
print(plen, u, vmin)
if pathes[vmin]: continue # 如果其最短路径已知则继续
pathes[vmin] = (u, plen) # 记录新确定的最短路径
for v, w in graph.out_edges(vmin): # 考察经由新 U 顶点的路径
if not pathes[v]: # 是到尚未知最短路径的顶点的路径，记录它
cands.enqueue((plen + w, vmin, v))
count += 1
return pathes
# Find all nearset pathes using Floyd-Warshall algorithm
def all_shortest_paths(graph):
vnum = graph.vertex_num()
a = [[graph.get_edge(i, j) for j in range(vnum)]
for i in range(vnum)] # create a copy the adjacent matrix
nvertex = [[-1 if a[i][j] == infinity else j
for j in range(vnum)]
for i in range(vnum)]
for k in range(vnum):
for i in range(vnum):
for j in range(vnum):
if a[i][j] > a[i][k] + a[k][j]:
a[i][j] = a[i][k] + a[k][j]
nvertex[i][j] = nvertex[i][k]
return (a, nvertex)
def test_dijkstra():
pathes0 = dijkstra_shortest_paths(g1, 0)
pathes1 = dijkstra_shortest_paths(g1, 1)
pathes2 = dijkstra_shortest_paths(g1, 2)
pathes3 = dijkstra_shortest_paths(g1, 3)
pathes4 = dijkstra_shortest_paths(g1, 4)
pathes5 = dijkstra_shortest_paths(g1, 5)
if (pathes0 != [(0, 0), (3, 41), (0, 10), (2, 25), (0, 45), None] or
pathes1 != [(2, 35), (1, 0), (1, 15), (2, 30), (1, 5), None] or
pathes2 != [(2, 20), (3, 31), (2, 0), (2, 15), (1, 36), None] or
pathes3 != [(2, 51), (3, 16), (1, 31), (3, 0), (1, 21), None] or
pathes4 != [(2, 81), (3, 46), (1, 61), (4, 30), (4, 0), None] or
pathes5 != [(2, 54), (3, 19), (1, 34), (5, 3), (1, 24), (5, 0)]):
print("Some result are not correct.")
print("start v0:", pathes0)
print("start v1:", pathes1)
print("start v2:", pathes2)
print("start v3:", pathes3)
print("start v4:", pathes4)
print("start v5:", pathes5)
# end test_dijkstra()
def test_floyd():
pathes = all_shortest_paths(g1)
print("")
print(pathes[0])
print(pathes[1])
if __name__ == '__main__':
gmat4 = [[ 0, 50, 10,inf, 45,inf],
[inf, 0, 15,inf, 5,inf],
[ 20,inf, 0, 15,inf,inf],
[inf, 16,inf, 0, 35,inf],
[inf,inf,inf, 30, 0,inf],
[inf,inf,inf, 3,inf, 0]]
g1 = GraphA(gmat4, inf)
test_dijkstra()
test_floyd()