[프로그래머스]Level.1 평균구하기

class Solution {
    public double solution(int[] arr) {
        double answer = 0;
        double average = 0;
        int sum = 0;
        
        for(int i=0; i< arr.length; i++){
            sum += arr[i];
        }
        
        average = (double) sum/ arr.length; 
        answer = average;
        return answer;
    }
}

O(n)