Reduce array size to the half

Array Hash Table Greedy Sorting Heap (Priority Queue)

69.3% acceptance

Feb 25, 2026

3362

153

You are given an integer array arr. You can choose a set of integers and remove all the occurrences of these integers in the array. Return the minimum size of the set so that at least half of the integers of the array are removed.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn min_set_size(arr: Vec<i32>) -> i32 {
    let n = arr.len();
    let mut freq: std::collections::HashMap<i32, usize> = std::collections::HashMap::new();
    for &x in &arr { *freq.entry(x).or_insert(0) += 1; }
    let mut counts: Vec<usize> = freq.values().copied().collect();
    counts.sort_unstable_by(|a, b| b.cmp(a));
    let mut removed = 0;
    let mut set_size = 0;
    for &c in &counts {
      removed += c;
      set_size += 1;
      if removed * 2 >= n { break; }
    }
    set_size
  }
}