2019东北赛补题之（E. Minimum Spanning Tree）贪心（伪最小生成树）

E. Minimum Spanning Tree

time limit per test

2.0 s

memory limit per test

512 MB

input

standard input

output

standard output

In the mathematical discipline of graph theory, the line graph of a simple undirected weighted graph GG is another simple undirected weighted graph L(G)L(G) that represents the adjacency between every two edges in GG.

Precisely speaking, for an undirected weighted graph GG without loops or multiple edges, its line graph L(G)L(G) is a graph such that:

• Each vertex of L(G)L(G) represents an edge of GG.
• Two vertices of L(G)L(G) are adjacent if and only if their corresponding edges share a common endpoint in GG, and the weight of such edge between this two vertices is the sum of their corresponding edges' weight.