设计一个验证系统

1. 题意

2. 分析

   • 给定tokenId，currentTime以及timeToLive，我们定义一个字典，存储的形式为dict[tokenId] = currentTime + timeToLive.
   • 在renew函数中，判断一下tokenId是否在字典的键中以及对应的值是否小于currentTime，如果都成立，则重置验证码，即dict[tokenId] = currentTime + timeToLive. 否则什么也不做。
   • 在countUnexpiredTokens函数中，定义一个变量res = 0, 依次遍历字典，如果字典中的值小于给定的currentTime，则res ++, 否则什么也不做。
   • 最后返回res即可。

3. 代码：

   • C++代码

   class AuthenticationManager {
   public:
       int timeToLive;
       unordered_map<string, int> mp;
       
       AuthenticationManager(int timeToLive) {
           this->timeToLive = timeToLive;
       }
       void generate(string tokenId, int currentTime) {
           mp[tokenId] = currentTime + timeToLive;
       }
       void renew(string tokenId, int currentTime) {
           if (mp.count(tokenId) && mp[tokenId] > currentTime){
               mp[tokenId] = currentTime + timeToLive;
           }
       }
       int countUnexpiredTokens(int currentTime) {
           int res = 0;
           for(auto &[_, time]: mp){
               if (time > currentTime) {
                   res ++;
               }
           }
           return res;
       }
   };
   
   /**
   * Your AuthenticationManager object will be instantiated and called as such:
   * AuthenticationManager* obj = new AuthenticationManager(timeToLive);
   * obj->generate(tokenId,currentTime);
   * obj->renew(tokenId,currentTime);
   * int param_3 = obj->countUnexpiredTokens(currentTime);
   */
   

   • python代码：

   class AuthenticationManager:
       def __init__(self, timeToLive: int):
           self.timeToLive = timeToLive
           self.mp = dict()
       def generate(self, tokenId: str, currentTime: int) -> None:
           self.mp[tokenId] = currentTime + self.timeToLive
       def renew(self, tokenId: str, currentTime: int) -> None:
           if tokenId in self.mp and self.mp[tokenId] > currentTime: self.mp[tokenId] = currentTime + self.timeToLive
       def countUnexpiredTokens(self, currentTime: int) -> int:
           res = 0
           for _, time in self.mp.items():
               if time > currentTime: res += 1
           return res
   # Your AuthenticationManager object will be instantiated and called as such:
   # obj = AuthenticationManager(timeToLive)
   # obj.generate(tokenId,currentTime)
   # obj.renew(tokenId,currentTime)
   # param_3 = obj.countUnexpiredTokens(currentTime)
   

4. 分析

   • 使用哈希表较为方便；
   • 模拟题。