Main.java

	private int[] a;
	private int[] b;

	/**
	 * @see <a href="https://v2ex.com/t/895464?p=2">see</a>
	 */
	public void calc(String[] input1, String[] input2) {
		a = Stream.of(input1).mapToInt(e -> new BigDecimal(e).multiply(BigDecimal.valueOf(100)).intValue()).sorted().toArray();
		b = Stream.of(input2).mapToInt(e -> new BigDecimal(e).multiply(BigDecimal.valueOf(100)).intValue()).sorted().toArray();
		if (IntStream.of(a).sum() != IntStream.of(b).sum()) {
			throw new IllegalArgumentException();
		}
		//多线程
		int n = Runtime.getRuntime().availableProcessors();
		for (int i = 0; i < n; i++) {
			int begin = i;
			new Thread(() -> {
				calc(new int[b.length], a[1], 1, begin, n);
			}, begin + ":" + n).start();
		}
		//单线程
//		calc(new int[b.length], a[1], 1, 0, 1);
	}

	private void calc(int[] bused, int s, int index, int begin, int step) {
		for (int i = begin; i < b.length; i += step) {
			if (bused[i] > 0) {
				continue;
			}
			if (i > 0 && b[i - 1] == b[i] && bused[i - 1] == 0) {
				continue;
			}
			if (b[i] > s) {
				break;
			} else {
				bused[i] = index;
				if (b[i] < s) {
					calc(bused, s - b[i], index, i + 1, 1);
				} else if (index + 1 < a.length) {
					calc(bused, a[index + 1], index + 1, 0, 1);
				} else {
					print(bused);
				}
				bused[i] = 0;
			}
		}
	}

	private synchronized void print(int[] bused) {
		System.out.println("result:");
		for (int j = 0; j < a.length; j++) {
			System.out.print(BigDecimal.valueOf(a[j]).divide(BigDecimal.valueOf(100)) + " = ");
			for (int k = 0; k < b.length; k++) {
				if (bused[k] == j) {
					System.out.print(BigDecimal.valueOf(b[k]).divide(BigDecimal.valueOf(100)) + " + ");
				}
			}
			System.out.println("\b\b\b");
		}
		System.exit(0);
	}