Python/dynamic_programming/floyd_warshall.py

43 lines
1.2 KiB
Python
Raw Normal View History

2018-10-19 12:48:28 +00:00
import math
2019-10-05 05:14:13 +00:00
2018-10-19 12:48:28 +00:00
class Graph:
def __init__(self, n=0): # a graph with Node 0,1,...,N-1
self.n = n
self.w = [
[math.inf for j in range(n)] for i in range(n)
2019-10-05 05:14:13 +00:00
] # adjacency matrix for weight
self.dp = [
[math.inf for j in range(n)] for i in range(n)
2019-10-05 05:14:13 +00:00
] # dp[i][j] stores minimum distance from i to j
2018-10-19 12:48:28 +00:00
def add_edge(self, u, v, w):
2018-10-19 12:48:28 +00:00
self.dp[u][v] = w
def floyd_warshall(self):
for k in range(self.n):
for i in range(self.n):
for j in range(self.n):
2018-10-19 12:48:28 +00:00
self.dp[i][j] = min(self.dp[i][j], self.dp[i][k] + self.dp[k][j])
def show_min(self, u, v):
2018-10-19 12:48:28 +00:00
return self.dp[u][v]
2019-10-05 05:14:13 +00:00
if __name__ == "__main__":
2018-10-19 12:48:28 +00:00
graph = Graph(5)
graph.add_edge(0, 2, 9)
graph.add_edge(0, 4, 10)
graph.add_edge(1, 3, 5)
graph.add_edge(2, 3, 7)
graph.add_edge(3, 0, 10)
graph.add_edge(3, 1, 2)
graph.add_edge(3, 2, 1)
graph.add_edge(3, 4, 6)
graph.add_edge(4, 1, 3)
graph.add_edge(4, 2, 4)
graph.add_edge(4, 3, 9)
2018-10-19 12:48:28 +00:00
graph.floyd_warshall()
graph.show_min(1, 4)
graph.show_min(0, 3)