Consider the language: A = { | G is a connected undirected graph} and consider the following algorithm to decide A:

M = "On input , the encoding of a graph G"

1.Select the first node of G and mark it.

2.Repeat the following stage until no new nodes are marked

---2a. For each node in G, mark it if it is attached by an edge to a node that is already marker

3. Scan all nodes of G to determine whether they are all marked. If they are, accept; otherwise, reject.

Please analyze this algorithm and compute the Big-O complexity.