Determine if a Graph is a Tree

You are given an undirected graph with n vertices and m edges. A graph is considered a tree if it meets the following criteria:

• The graph is connected.
• The graph contains exactly \( n-1 \) edges.
• The graph does not contain any cycles.

Your task is to determine whether the given graph is a tree. In other words, check if the input graph is connected and has no cycles while having exactly \( n-1 \) edges.

inputFormat

The input begins with an integer T denoting the number of test cases. Each test case starts with a line containing two integers n and m — the number of vertices and the number of edges, respectively. The next m lines each contain two integers representing an undirected edge between two vertices.

outputFormat

For each test case, output a single line: "YES" if the provided graph is a tree, or "NO" otherwise.

## sample

1
4 3
1 2
2 3
3 4

YES

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