[Codility] Counting Elements - MaxCounters / Java

1. 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:

class Solution { public int[] solution(int N, int[] A); }

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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2. 코드

class Solution {
    public int[] solution(int N, int[] A) {
        // write your code in Java SE 8
        int[] result = new int[N];
        
        int max = 0;
        int globalMax = 0;
        for(int i=0; i<A.length; i++) {
            if(A[i] > N) {
                globalMax = max;
            } else {
                if(result[A[i]-1] < globalMax)
                    result[A[i]-1] = globalMax + 1;
                else
                    result[A[i]-1]++;
                    
                max = Math.max(max, result[A[i]-1]);
            }
        }
        
        for(int i=0; i<result.length; i++) {
            if(result[i] < globalMax) {
                result[i] = globalMax;
            }
                
        }
        return result;
    }
}