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2424. Longest Uploaded Prefix 👍

  • Time: Constructor: $O(1)$, upload(video: int): $O(1)$,longest()`: $O(1)$
  • Space: $O(|\texttt{upload()}|)$
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class LUPrefix {
 public:
  LUPrefix(int n) {}

  void upload(int video) {
    seen.insert(video);
    while (seen.count(longestPrefix + 1))
      ++longestPrefix;
  }

  int longest() {
    return longestPrefix;
  }

 private:
  unordered_set<int> seen;
  int longestPrefix = 0;
};

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class LUPrefix {
  public LUPrefix(int n) {}

  public void upload(int video) {
    seen.add(video);
    while (seen.contains(longestPrefix + 1))
      ++longestPrefix;
  }

  public int longest() {
    return longestPrefix;
  }

  private Set<Integer> seen = new HashSet<>();
  private int longestPrefix = 0;
}

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class LUPrefix:
  def __init__(self, n: int):
    self.seen = set()
    self.longestPrefix = 0

  def upload(self, video: int) -> None:
    self.seen.add(video)
    while self.longestPrefix + 1 in self.seen:
      self.longestPrefix += 1

  def longest(self) -> int:
    return self.longestPrefix