Boleyn Salary – HackerRank Solution

In this post, we will solve Boleyn Salary HackerRank Solution. This problem (Boleyn Salary) is a part of HackerRank Functional Programming series.

Task

Boleyn Su runs a company called Acme. There are N employees in the company, and each one of them is represented by a unique employee id whose range lies in [1, N]. Being the head of company, Boleyn’s employee id is 1.

Each employee, except Boleyn, has exactly one direct superior. This means that the hierarchial structure of the company is like a tree, where

1. Boleyn, employee id 1, represents the root node.
2. Each pair of employee is directly or indirectly connected to one another.
3. There is no cycle.

Let’s represent the salary by the array s = {s[1], s[2], s[3]…, s[N]}, where s[i] is the salary of the i^th employee. Salary structure in the company is non-uniform. Even a subordinate may get a higher salary than her superior. Some of the employees in Acme are curious about who gets the k^th lowest salary among her subordinates. Help them in solving their query.

Note

1. 1^st lowest salary is equivalent to lowest salary, 2^nd lowest means lowest salary which is greater that 1^st lowest salary, and so on.
2. Salary of each employee is different.
3. It is not necessary that the people who are placed higher on hierarchy will have a greater salary than their subordinates.

Input Format

The first line contains two space separated integers, N Q, where N is the number of employees in Acme, and Q is the number of queries.
Then follows N-1 lines. Each of these lines contain two space separated integers, u p, where p is the superior of u. u and p are employees id.
In the next line there are N space separated integers, s[1] s[2] … s[n], where s[i], i ∈ [1..N], is the salary of i^th employee.
Then, Q queries follow. Each query contains two space separated integers, v k. See output format for it’s definition.

Output Format

For the first query, print the id of employee who has the k^th lowest salary among the subordinates of v.
For the subsequent queries, we need to find the k^th lowest salary of the subordinates of v+d, where d is the answer of previous query.

Constraints

• 1 ≤ N ≤ 3*10⁴
• 1 ≤ Q ≤ 3*10⁴
• 1 ≤ s[i] ≤ 10⁹, i ∈ [1..N]
• s[i] ≠ s[j], 1 ≤ i < j ≤ N
• 1 ≤ u, p ≤ N, u ≠ p
• -N ≤ d ≤ N
• For 1^st query, 1 ≤ v ≤ N
• For later queries, 1 ≤ v+d ≤ N
• For each query, 1 ≤ K ≤ Number_of_subordinates

Sample Input

8 7
2 1
3 2
4 2
7 4
8 4
5 1
6 5
70 40 60 80 10 20 30 50
2 1
-6 5
-4 1
-5 3
2 1
-5 4
2 2

Sample Output

7
8
7
3
6
2
8

Explanation

Tree structure will be

         1(70)
        / \
       /   \
    2(40)  5(10)
     / \      \
    /   \      \
 3(60)  4(80)  6(20)
         / \
        /   \
     7(30)  8(50)

Query #1 Node = 2, k = 1: Subordinates, in increasing order of salary, are (7, 30), (8, 50), (3, 60), (4, 80). So employee 7 has the 1^st lowest salary among the subordinates of 2.
Query #2 Node = -6+7 = 1, k = 5: Subordinates are (5, 10), (6, 20), (7, 30), (2, 40), (8, 50), (3, 60), (4, 80) . 8^th employee has the 5^th lowest salary among the subordinate of 1.
Query #3 Node = -4+8 = 4, k = 1: Subordinates are (7, 30), (8, 50) . Similarly 7 is the answer of this query.
Query #4 Node = -5+7 = 2, k = 3: Subordinates are (7, 30), (8, 50), (3, 60), (4, 80). Similarly 3 is the answer for this query.
Query #5 Node = 2+3 = 5, k = 1: Subordinates are (6, 20). 6^th employee has the most, and only, lowest salary.
Query #6 Node = -5+6 = 1, k = 4: Subordinates are (5, 10), (6, 20), (7, 30), (2, 40), (8, 50), (3, 60), (4, 80). 2 is answer of this query.
Query #7 Node = 2+2 = 4, k = 2: Subordinates are (7, 30), (8, 50). Employee 8 has the second lowest salaries among the subordinates of 4.

Solution – Boleyn Salary – HackerRank Solution

Scala

import java.util.Scanner

import scala.collection.immutable.TreeMap

object Solution {
  def main(args: Array[String]): Unit = {
    val sc = new Scanner(System.in)

    val n = sc.nextInt
    val q = sc.nextInt

    val links = (0 until n - 1).map(_ => (sc.nextInt, sc.nextInt))
      .groupBy(_._2)
      .map { case (key, list) => key -> list.map(_._1) }
    val salaries = (0 until n).map(_ => sc.nextInt)

    case class Node(index: Int, count: Int, children: Seq[Node], data: TreeMap[Int, Int])

    val nodes = Array.ofDim[Node](n + 1)

    def create(index: Int): Node = {
      val children = links.get(index) match {
        case None => Nil
        case Some(v) => v.map(create)
      }

      val sortedChildren = children.sortBy(-_.count)
      val data = if (children.isEmpty) TreeMap[Int, Int]() else
        sortedChildren.tail.foldLeft(sortedChildren.head.data + (salaries(sortedChildren.head.index - 1) -> sortedChildren.head.index))(
          (acc, c) => acc ++ c.data + (salaries(c.index - 1) -> c.index)
        )

      val res = Node(index, children.map(_.count).sum, children, data)
      nodes(index) = res
      res
    }

    create(1)

    var answer = 0
    (0 until q).foreach(_ => {
      val v = sc.nextInt
      val k = sc.nextInt

      val id = answer + v

      answer = nodes(id).data.drop(k - 1).values.head
      println(answer)
    })
  }
}

Note: This problem (Boleyn Salary) is generated by HackerRank but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.