89 lines
2.4 KiB
Python
89 lines
2.4 KiB
Python
from math import inf
|
|
from typing import Iterator, Optional
|
|
|
|
|
|
class Node:
|
|
def __init__(self, x: int, y: int):
|
|
self.x: int = x
|
|
self.y: int = y
|
|
|
|
|
|
class Edge:
|
|
def __init__(self, start: int, end: int, length: float):
|
|
self.length: float = length
|
|
self.start: int = start
|
|
self.end: int = end
|
|
|
|
|
|
class Graph:
|
|
def __init__(self):
|
|
self.edges: list[Edge] = []
|
|
self.nodes: list[Node] = []
|
|
|
|
def add_node(self, x: int, y: int) -> None:
|
|
self.nodes.append(Node(x, y))
|
|
|
|
def add_edge(self, start_index: int, end_index: int, length: float) -> None:
|
|
self.edges.append(Edge(start_index, end_index, length))
|
|
|
|
def edges_adjacent_to(self, node_i: int) -> Iterator[Edge]:
|
|
return filter(lambda e: e.start == node_i or e.end == node_i, self.edges)
|
|
|
|
def dijkstra(self, source_index: int, target_index: int) -> Optional[list[int]]:
|
|
n = len(self.nodes)
|
|
|
|
if source_index < 0 or source_index >= n:
|
|
return None
|
|
|
|
if target_index < 0 or target_index >= n:
|
|
return None
|
|
|
|
unvisited = list(range(n))
|
|
|
|
distances_from_start = [inf] * n
|
|
distances_from_start[source_index] = 0
|
|
|
|
node_sequences = [[] for _ in range(n)]
|
|
node_sequences[source_index] = [source_index]
|
|
|
|
while True:
|
|
current_index = min(unvisited, key=lambda i: distances_from_start[i])
|
|
|
|
if current_index == target_index:
|
|
break
|
|
|
|
unvisited.remove(current_index)
|
|
|
|
for edge in self.edges_adjacent_to(current_index):
|
|
start = current_index
|
|
end = edge.end if edge.start == current_index else edge.start
|
|
|
|
if end in unvisited and distances_from_start[end] > distances_from_start[start] + edge.length:
|
|
distances_from_start[end] = distances_from_start[start] + edge.length
|
|
node_sequences[end] = node_sequences[start].copy()
|
|
node_sequences[end].append(end)
|
|
|
|
return node_sequences[target_index]
|
|
|
|
|
|
def main() -> None:
|
|
graph = Graph()
|
|
|
|
graph.add_node(1, 2)
|
|
graph.add_node(4, 7)
|
|
graph.add_node(3, 1)
|
|
graph.add_node(-2, 0)
|
|
graph.add_node(0, 0)
|
|
|
|
graph.add_edge(0, 1, 1)
|
|
graph.add_edge(1, 2, 2)
|
|
graph.add_edge(2, 3, 3)
|
|
graph.add_edge(3, 0, 1)
|
|
graph.add_edge(1, 3, 3)
|
|
|
|
print(graph.dijkstra(0, 3))
|
|
|
|
|
|
if __name__ == "__main__":
|
|
main()
|