[Level 2] 타겟 넘버

class Solution {
    public int answer = 0;
    
    public int solution(int[] numbers, int target) {
        recur(0, numbers, 0, target);
        
        return answer;
    }
    
    public void recur(int index, int[] numbers, int sum, int target) {
        if(index==numbers.length) {
            if(sum==target) { answer++; }
            
            return;
        }
        
        recur(index+1, numbers, sum+numbers[index], target);
        recur(index+1, numbers, sum-numbers[index], target);
    }
}