def singleSourceShortest(G, src):
"""
Given graph G return dictionary of shortest paths to other vertices
from vertex src. All vertices in G must be drawn from the range 0..n-1
and src must also be from same range.
"""
# Initialize dist[] matrix to be Infinity for all but src
infinity = sys.maxsize
n = 0
dist = {}
for v in range(len(G)):
n += 1
dist[v] = infinity
dist[src] = 0
# optimized construction for BinaryHeap
pq = BinaryHeap(n, src, infinity)
while not pq.isEmpty():
u = pq.pop()
for v, weight in G.neighbors(u):
newLen = dist[u] + weight
if newLen < dist[v]:
pq.decreaseKey(v, newLen)
dist[v] = newLen
return dist
def singleSourceShortest(G, src):
"""
Given graph G return dictionary of shortest paths to other vertices
from vertex src. All vertices in G must be drawn from the range 0..n-1
and src must also be from same range.
"""
# Initialize dist[] matrix to be Infinity for all but src
infinity = sys.maxsize
n = 0
dist = {}
for v in range(len(G)):
n += 1
dist[v] = infinity
dist[src] = 0
# optimized construction for BinaryHeap
pq = BinaryHeap(n, src, infinity)
while not pq.isEmpty():
u = pq.pop()
for v,weight in G.neighbors(u):
newLen = dist[u] + weight
if newLen < dist[v]:
pq.decreaseKey(v, newLen)
dist[v] = newLen
return dist
class TestBinaryHeap(unittest.TestCase):
def setUp(self):
# create BinaryHeap with initial 4 elements, and src is 2. Use
# 999 for infinity
self.bh = BinaryHeap(15,2,999)
def tearDown(self):
self.bh = None
def test_basic(self):
self.assertEqual(2, self.bh.pop())
def test_decreaseKey(self):
self.bh.decreaseKey(0, 19)
self.bh.decreaseKey(1, 7)
self.bh.decreaseKey(3,22)
self.assertEqual(2, self.bh.pop())
self.assertEqual(1, self.bh.pop())
self.assertEqual(0, self.bh.pop())
self.assertEqual(3, self.bh.pop())
def test_decreaseKeyMany(self):
self.bh = BinaryHeap(1000,0,999)
for _ in range(999, 0, -1):
self.bh.decreaseKey(_, _)
for _ in range(1000):
self.assertEqual(_, self.bh.pop())
def test_multipleDecreaseKey(self):
self.bh = BinaryHeap(50,0,999)
for n in range(1, 50):
for p in range(1, n):
self.bh.decreaseKey(n, p)
result = []
for _ in range(50):
result.append(self.bh.pop())
self.assertEqual(list(range(50)), sorted(result))
def test_decreaseKeyRandom(self):
self.bh = BinaryHeap(1000,0,999)
for _ in range(999, 0, -1):
self.bh.decreaseKey(_, random.randint(1,999))
result = []
for _ in range(1000):
result.append(self.bh.pop())
self.assertEqual(list(range(1000)), sorted(result))