2026/02/28

[LeetCode] 128 Longest Consecutive Sequence

 練習使用unordered set

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class Solution {
public:
  int longestConsecutive(vector<int>& Nums) {
    std::unordered_set<int> numSet;
    for (auto &num : Nums)
      numSet.insert(num);

    int ans = 0;
    for (auto &num : Nums) {
      int next = 1;
      while (numSet.count(num + next)) {
        numSet.erase(num + next);
        next++;
      }

      int prev = 1;
      while (numSet.count(num - prev)) {
        numSet.erase(num - prev);
        prev++;
      }

      ans = max(ans, next + prev - 1);
    }
    return ans;
  }
};
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