def __init__(self, EG):
self._edgeTo = [-1 for _ in range(EG.V())]
self._distTo = [_INF for _ in range(EG.V())]
self._distTo[0] = 0
self._pq = IndexMinPQ(EG.V())
self._mst = [] # list of edges in MST
self._weight = 0
self._marked = set() # set of vertices in MST
self._pq.insert(0, 0)
while (not self._pq.isEmpty() and len(self._mst) < EG.V() - 1):
v = self._pq.delMin()
if v > 0:
self._mst.append(self._edgeTo[v])
self._weight += self._edgeTo[v].weight()
self._visit(EG, v)
def __init__(self, G, s, t=None):
"find the shortest path tree (in a directed graph with non-negative weights) from s to every other vertex using Dijkstra's alg"
self._s = s
self._distTo = [_INF for _ in range(G.V())]
self._distTo[s] = 0
self._edgeTo = [_SENTINEL for _ in range(G.V())
] # edgeTo[v]: last edge on shortest path from s to v
self._pq = IndexMinPQ(G.V())
self._pq.insert(s, 0)
while (not self._pq.isEmpty()):
v = self._pq.delMin() # add closest vertex to source to Tree
if t and v == t: return
for e in G.adj(v):
self._relax(
e
) # relax(e) updates the distTo and edgeTo data structures
