滑动窗口 class Solution { public: /** * * @param arr int整型vector the array * @return int整型 */

int maxLength(vector<int>& arr) {
    // write code here
    unordered_set<int>s;
    int i = 0,j = 0;
    int ret = 0;
    while(j < arr.size())
    {
        if(s.find(arr[j]) != s.end())
        {
            s.erase(arr[i]);
            i++;
        }else
        {
            s.insert(arr[j]);
            ret = s.size() > ret ?s.size() : ret;
            j++;
        }
    }
    return ret;
}

};