思考题 for no one

Tour

You are given a tree of N nodes. Given another integer array A of length M.

Little CMJ chooses M sequences of nodes. The i-th of them is and he chooses them so that for each ,there's an edge from to , and . Then he set all the nodes in the sequences "visited"

Can all the nodes be visited after choosing the M sequences?

Example

Example 1

Tree={[1,2],[2,3],[2,4],[4,7],[1,5],[1,6]}
M={3,4,2,2}

Answer:
YES

Explain:
tree
{1,2,3} {1,2,4,7} {1,5} {1,6} is chosen

Example 2

Tree={[1,2],[2,3],[2,4],[4,7],[1,5],[1,6]}
M={6,2,2}

Answer:
YES

Explain:
{1,2,3,2,4,7} {1,5} {1,6} is chosen

Example 3

Tree={[1,2],[2,3],[2,4],[4,7],[1,5],[1,6]}
M={9}

Answer:
NO

Explain:
if M={10}, then possible: {1,5,1,6,1,2,3,2,4,7}