깊이/너비 우선 탐색
function solution(numbers, target) {
let answer = 0;
const length = numbers.length;
const dfs = (depth, ac) => {
if(depth < length) {
dfs(depth + 1, ac + numbers[depth]);
dfs(depth + 1, ac - numbers[depth]);
} else {
if(ac === target) {
answer++;
}
}
}
dfs(0, 0);
return answer;
}