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3450. Maximum Students on a Single Bench 👍

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  int maxStudentsOnBench(vector<vector<int>>& students) {
    constexpr int kMax = 100;
    size_t ans = 0;
    vector<unordered_set<int>> benchToStudents(kMax + 1);

    for (const vector<int>& student : students) {
      const int studentId = student[0];
      const int benchId = student[1];
      benchToStudents[benchId].insert(studentId);
    }

    for (const unordered_set<int>& students : benchToStudents)
      ans = max(ans, students.size());

    return ans;
  }
};

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class Solution {
  public int maxStudentsOnBench(int[][] students) {
    final int MAX = 100;
    int ans = 0;
    Set<Integer>[] benchToStudents = new Set[MAX + 1];

    for (int i = 0; i <= MAX; ++i)
      benchToStudents[i] = new HashSet<>();

    for (int[] student : students) {
      final int studentId = student[0];
      final int benchId = student[1];
      benchToStudents[benchId].add(studentId);
    }

    for (Set<Integer> studentsOnBench : benchToStudents)
      ans = Math.max(ans, studentsOnBench.size());

    return ans;
  }
}

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class Solution:
  def maxStudentsOnBench(self, students: list[list[int]]) -> int:
    benchToStudents = collections.defaultdict(set)
    for studentId, benchId in students:
      benchToStudents[benchId].add(studentId)
    return max(map(len, benchToStudents.values()), default=0)