不同的好子序列数目

/*
 * 思路：
 * 使用Java Stream API进行操作。主要思想与普通Java代码类似，只是使用流操作来简化处理。
 */

import java.util.stream.IntStream;

public class GoodSubsequencesStream {
    private static final int MOD = 1000000007;

    public int numberOfUniqueGoodSubsequences(String binary) {
        int n = binary.length();
        long[] counts = {0, 0}; // counts[0]表示0的数量，counts[1]表示1的数量
        boolean has0 = binary.contains("0");

        IntStream.range(0, n).forEach(i -> {
            char c = binary.charAt(i);
            if (c == '1') {
                counts[1] = (counts[0] + counts[1] + 1) % MOD;
            } else {
                counts[0] = (counts[0] + counts[1]) % MOD;
            }
        });

        return (int) ((counts[1] + (has0 ? 1 : 0)) % MOD);
    }

    public static void main(String[] args) {
        GoodSubsequencesStream gs = new GoodSubsequencesStream();
        System.out.println(gs.numberOfUniqueGoodSubsequences("001")); // Output: 2
        System.out.println(gs.numberOfUniqueGoodSubsequences("11"));  // Output: 2
        System.out.println(gs.numberOfUniqueGoodSubsequences("101")); // Output: 5
    }
}