「力扣」第 5409 题：检查一个字符串是否包含所有长度为 K 的二进制子串（滑动窗口、位运算、哈希表）

Java 代码：

import java.util.HashSet;
import java.util.Set;

public class Solution {

    public boolean hasAllCodes(String s, int k) {
        int len = s.length();
        if (len < k) {
            return false;
        }

        char[] charArray = s.toCharArray();

        int num = 1 << k;
        Set<Integer> hashSet = new HashSet<>();
        for (int i = 0; i < num; i++) {
            hashSet.add(i);
        }

        int window = 0;
        for (int i = 0; i < k; i++) {
            window += (charArray[i] - '0') * (1 << (k - i - 1));
        }

        for (int i = 0; i < len - k; i++) {
            if (window >= num) {
                return false;
            }
            hashSet.remove(window);

            window -= (charArray[i] - '0') * (1 << (k - 1));
            window <<= 1;
            window += (charArray[i + k] - '0');
        }

        hashSet.remove(window);
        return window <= num && hashSet.size() == 0;
    }

    public static void main(String[] args) {
        Solution solution = new Solution();
//        String s = "00110110";
//        int k = 2;

//        String s = "00110";
//        int k = 2;

//        String s = "0110";
//        int k = 1;

//        String s = "0110";
//        int k = 2;

//        String s = "0000000001011100";
//        int k = 4;

        String s = "0101";
        int k = 13;

        boolean res = solution.hasAllCodes(s, k);
        System.out.println(res);
    }
}