# Minimum Spanning Tree problem is in NP
Last edited: 2025-12-05
# Statement
Lemma
# Proof
The problem is in the correct form for a search problem . It outputs a MST always as one always exists from the definition.
To verify a solution as we can first check it is a spanning tree by running BFS to verify it is connected and checking the size of the edge set is $\vert V \vert - 1$ to check it is a tree. To check it is minimal we can find a solution in polynomial time using Kruskal’s algorithm . We can just check it’s weight vs the weight of the proposed solution to check they match.