Maximum students on a single bench

Array Hash Table

87.9% acceptance

Mar 31, 2026

You are given a 2D integer array of student data students, where students[i] = [student_id, bench_id] represents that student student_id is sitting on the bench bench_id. Return the maximum number of unique students sitting on any single bench. If no students are present, return 0. Note: A student can appear multiple times on the same bench in the input, but they should be counted only once per bench.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

use std::collections::{HashMap, HashSet};

impl Solution {
  pub fn max_students_on_bench(students: Vec<Vec<i32>>) -> i32 {
    let mut bench_map: HashMap<i32, HashSet<i32>> = HashMap::new();
    for s in &students {
      bench_map.entry(s[1]).or_default().insert(s[0]);
    }
    bench_map.values().map(|s| s.len() as i32).max().unwrap_or(0)
  }
}