Minimum operations to collect elements

Array Hash Table Bit Manipulation

62.2% acceptance

Feb 25, 2026

210

You are given an array nums of positive integers and an integer k. In one operation, you can remove the last element of the array and add it to your collection. Return the minimum number of operations needed to collect elements 1, 2, ..., k.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn min_operations(nums: Vec<i32>, k: i32) -> i32 {
    let n = nums.len();
    let mut collected = vec![false; (k + 1) as usize];
    let mut count = 0;
    let need = k as usize;
    for i in (0..n).rev() {
      let v = nums[i] as usize;
      if v <= need && !collected[v] {
        collected[v] = true;
        count += 1;
      }
      if count == need {
        return (n - i) as i32;
      }
    }
    n as i32
  }
}