Python/graphs/minimum_spanning_tree_kruskal.py

from __future__ import print_function

if __name__ == "__main__":
    num_nodes, num_edges = list(map(int, input().strip().split()))

    edges = []

    for i in range(num_edges):
	    node1, node2, cost = list(map(int, input().strip().split()))
	    edges.append((i,node1,node2,cost))

    edges = sorted(edges, key=lambda edge: edge[3])

    parent = list(range(num_nodes))

    def find_parent(i):
	    if i != parent[i]:
		    parent[i] = find_parent(parent[i])
	    return parent[i]

    minimum_spanning_tree_cost = 0
    minimum_spanning_tree = []

    for edge in edges:
	    parent_a = find_parent(edge[1])
	    parent_b = find_parent(edge[2])
	    if parent_a != parent_b:
		    minimum_spanning_tree_cost += edge[3]
		    minimum_spanning_tree.append(edge)
		    parent[parent_a] = parent_b

    print(minimum_spanning_tree_cost)
    for edge in minimum_spanning_tree:
	    print(edge)