查找一个数等于一组数中某些数相加的和

实现需求:

查找一个数等于一组数中哪些数相加的和

例如: 从1, 2, 3, 4, 5, 6, 7 中找出和为5的数, 即2, 3

public class AccumulationUtil {

    private AccumulationUtil(){}

    private static final Logger logger = LoggerFactory.getLogger(AccumulationUtil.class);

    public static void main(String[] args) {
        long temp[] = {1L, 2L, 3L, 4L, 5L, 6L, 7L};
        List<Long> newList = getNewList(temp, 5);
        System.out.println(newList);
    }

    /**
     * 查找一个数等于一组数中哪些数相加的和
     * @param keys
     * @param target
     * @return
     */
    public static List<Long> getNewList(long[] keys, long target) {
        int n = keys.length;
        int nbit = 1 << n;
        long in;
        List<Long> list = new ArrayList<>();
        for (int i = 0; i < nbit; i++) {
            in = 0;
            list.clear();
            for (int j = 0; j < n; j++) {
                int tmp = 1 << j; // 由0到n右移位
                if ((tmp & i) != 0) { // 与运算，同为1时才会是1
                    in += keys[j];
                    list.add(keys[j]);
                }
            }
            if (in == target){
                return list;
            }
        }
        return Collections.emptyList();
    }
}