Star or Not

AtCoder

IDabc225_b

Time2000ms

Memory256MB

Difficulty—

You are given a tree with $N$ vertices and $N-1$ edges. The vertices are numbered $1,2,\ldots,N$. The $i$\-th edge connects Vertex $a_i$ and Vertex $b_i$. Determine whether this tree is a star. Here, a star is a tree where there is a vertex directly connected to all other vertices. ## Constraints * $3 \leq N \leq 10^5$ * $1 \leq a_i \lt b_i \leq N$ * The given graph is a tree. ## Input Input is given from Standard Input in the following format: $N$ $a_1$ $b_1$ $\vdots$ $a_{N-1}$ $b_{N-1}$ [samples] ## Notes For the definition of a tree, see [Tree (graph theory) - Wikipedia](https://en.wikipedia.org/wiki/Tree_(graph_theory)).

Samples

Input #1

Output #1

Yes

The given graph is a star.

Input #2

Output #2

No

The given graph is not a star.

Input #3

Output #3

Yes

API Response (JSON)

{
  "problem": {
    "name": "Star or Not",
    "description": {
      "content": "You are given a tree with $N$ vertices and $N-1$ edges.   The vertices are numbered $1,2,\\ldots,N$. The $i$\\-th edge connects Vertex $a_i$ and Vertex $b_i$. Determine whether this tree is a star. Here",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc225_b"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "You are given a tree with $N$ vertices and $N-1$ edges.  \nThe vertices are numbered $1,2,\\ldots,N$. The $i$\\-th edge connects Vertex $a_i$ and Vertex $b_i$.\nDetermine whether this tree is a star.\nHere...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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