Count Descendants

AtCoder

IDabc202_e

Time2000ms

Memory256MB

Difficulty—

We have a rooted tree with $N$ vertices, numbered $1, 2, \dots, N$. Vertex $1$ is the root, and the parent of Vertex $i \, (2 \leq i \leq N)$ is Vertex $P_i$. You are given $Q$ queries. In the $i$\-th query $(1 \leq i \leq Q)$, given integers $U_i$ and $D_i$, find the number of vertices $u$ that satisfy all of the following conditions: * Vertex $U_i$ is in the shortest path from $u$ to the root (including the endpoints). * There are **exactly** $D_i$ edges in the shortest path from $u$ to the root. ## Constraints * $2 \leq N \leq 2 \times 10^5$ * $1 \leq P_i < i$ * $1 \leq Q \leq 2 \times 10^5$ * $1 \leq U_i \leq N$ * $0 \leq D_i \leq N - 1$ * All values in input are integers. ## Input Input is given from Standard Input in the following format: $N$ $P_2$ $P_3$ $\ldots$ $P_N$ $Q$ $U_1$ $D_1$ $U_2$ $D_2$ $\vdots$ $U_Q$ $D_Q$ [samples]

Samples

Input #1

7
1 1 2 2 4 2
4
1 2
7 2
4 1
5 5

Output #1

3
1
0
0

In the $1$\-st query, Vertices $4$, $5$, and $7$ satisfy the conditions. In the $2$\-nd query, only Vertices $7$ satisfies the conditions. In the $3$\-rd and $4$\-th queries, no vertice satisfies the conditions.
![image](https://img.atcoder.jp/ghi/abc202_e_sample_00.jpg)

API Response (JSON)

{
  "problem": {
    "name": "Count Descendants",
    "description": {
      "content": "We have a rooted tree with $N$ vertices, numbered $1, 2, \\dots, N$. Vertex $1$ is the root, and the parent of Vertex $i \\, (2 \\leq i \\leq N)$ is Vertex $P_i$. You are given $Q$ queries. In the $i$\\-th",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc202_e"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "We have a rooted tree with $N$ vertices, numbered $1, 2, \\dots, N$.\nVertex $1$ is the root, and the parent of Vertex $i \\, (2 \\leq i \\leq N)$ is Vertex $P_i$.\nYou are given $Q$ queries. In the $i$\\-th...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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