[codility] Counting Elements - MaxCounters

문제

You are given N counters, initially set to 0, and you have two possible operations on them:

• increase(X) − counter X is increased by 1,
• max counter − all counters are set to the maximum value of any counter.

A non-empty array A of M integers is given. This array represents consecutive operations:

• if A[K] = X, such that 1 ≤ X ≤ N, then operation K is increase(X),
• if A[K] = N + 1 then operation K is max counter.

For example, given integer N = 5 and array A such that:

A[0] = 3 A[1] = 4 A[2] = 4 A[3] = 6 A[4] = 1 A[5] = 4 A[6] = 4

the values of the counters after each consecutive operation will be:

(0, 0, 1, 0, 0) (0, 0, 1, 1, 0) (0, 0, 1, 2, 0) (2, 2, 2, 2, 2) (3, 2, 2, 2, 2) (3, 2, 2, 3, 2) (3, 2, 2, 4, 2)

The goal is to calculate the value of every counter after all operations.

Write a function:

public func solution(_ N : Int, _ A : inout [Int]) -> [Int]

that, given an integer N and a non-empty array A consisting of M integers, returns a sequence of integers representing the values of the counters.

Result array should be returned as an array of integers.

For example, given:

A[0] = 3 A[1] = 4 A[2] = 4 A[3] = 6 A[4] = 1 A[5] = 4 A[6] = 4

the function should return [3, 2, 2, 4, 2], as explained above.

Write an efficient algorithm for the following assumptions:

• N and M are integers within the range [1..100,000];
• each element of array A is an integer within the range [1..N + 1].
  
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문제 해설

A[K] = X, 1 <= X <= N 카운트 증가

A[K] = N + 1 이면 최대 카운트값 전체적용

 

구현 해설

X값이 1보다 크거나 같고 N보다 작거나 같으면 해당 인덱스 카운팅 값 증가

큰값이나 예측하지 못한 데이터가 들어오는 경우가 발생

arr 에 현재 카운팅중 가장 큰값을 초기화하는 [Int](repeating: arr.max()!, count: N) 구문인듯 하다.

다른 방법으로 계속 풀어봤으나 100%는 힘들어서 검색을 해봄

 

https://app.codility.com/demo/results/trainingC62947-485/

import Foundation
import Glibc

// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")

public func solution(_ N : Int, _ A : inout [Int]) -> [Int] {
    // write your code in Swift 4.2.1 (Linux)
    var arr = [Int](repeating: 0, count: N)
    for (index, _) in A.enumerated() {
        if 1 <= A[index] && A[index] <= N  {
            arr[A[index]-1] += 1
        } else if A[index] == N+1 {
            arr = [Int](repeating: arr.max()!, count: N)
        }
    }
    
    return arr
}

 

해결 힌트는 return 시 maxCounter와 arr에 카운트값과 비교하여 작은 값에 초기화

 

https://app.codility.com/demo/results/trainingWYS26A-946/

import Foundation
import Glibc

// you can write to stdout for debugging purposes, e.g.
// print("this is a debug message")

public func solution(_ N : Int, _ A : inout [Int]) -> [Int] {
    // write your code in Swift 4.2.1 (Linux)
    var arr = [Int](repeating: 0, count: N)
        
    var max = 0
    var maxCounter = 0
    for (index, _) in A.enumerated() {
        if A[index] > N {
            maxCounter = max
        } else {
            if arr[A[index]-1] < maxCounter {
                arr[A[index]-1] = maxCounter
            }
                
            arr[A[index]-1] += 1
                
            if max < arr[A[index]-1] {
                max = arr[A[index]-1]
            }
        }
    }
    return arr.map({ $0 < maxCounter ? maxCounter : $0 })
}