LeetCode 567. 字符串的排列-滑动窗口法-Java 解答

================ 567. 字符串的排列 ================
class Solution {
    public boolean checkInclusion(String s1, String s2) {
        HashMap need = new HashMap<>();
        HashMap window = new HashMap<>();
        for (int i = 0;i= s1.length()){
                //在这里判断是否找到了合法的子串
                if (valid == need.size()){
                    return true;
                }
                char d = s2.charAt(left);
                left++;
                //进行窗口内数据的一系列更新
                if(need.containsKey(d)){
                    if(window.get(d).equals(need.get(d))){
                        valid--;
                    }
                    window.put(d,window.getOrDefault(d,0)-1);
                }
            }
        }
        return false;
    }
}