1673. Find the Most Competitive Subsequence

Given an integer array nums and a positive integer k, return the most competitive subsequence of nums of size k.

An array's subsequence is a resulting sequence obtained by erasing some (possibly zero) elements from the array.

We define that a subsequence a is more competitive than a subsequence b (of the same length) if in the first position where a and b differ, subsequence a has a number less than the corresponding number in b. For example, [1,3,4] is more competitive than [1,3,5] because the first position they differ is at the final number, and 4 is less than 5.

 

Example 1:

Input: nums = [3,5,2,6], k = 2
Output: [2,6]
Explanation: Among the set of every possible subsequence: {[3,5], [3,2], [3,6], [5,2], [5,6], [2,6]}, [2,6] is the most competitive.

Example 2:

Input: nums = [2,4,3,3,5,4,9,6], k = 4
Output: [2,3,3,4]

 

Constraints:

  • 1 <= nums.length <= 105
  • 0 <= nums[i] <= 109
  • 1 <= k <= nums.length

Rust Solution

struct Solution;

impl Solution {
    fn most_competitive(nums: Vec<i32>, k: i32) -> Vec<i32> {
        let n = nums.len();
        let k = k as usize;
        let mut arr = vec![];
        let mut m = 0;
        for i in 0..n {
            while let Some(&top) = arr.last() {
                if top > nums[i] && k < n - m {
                    m += 1;
                    arr.pop();
                } else {
                    break;
                }
            }
            arr.push(nums[i]);
        }
        arr[0..k].to_vec()
    }
}

#[test]
fn test() {
    let nums = vec![3, 5, 2, 6];
    let k = 2;
    let res = vec![2, 6];
    assert_eq!(Solution::most_competitive(nums, k), res);
    let nums = vec![2, 4, 3, 3, 5, 4, 9, 6];
    let k = 4;
    let res = vec![2, 3, 3, 4];
    assert_eq!(Solution::most_competitive(nums, k), res);
}

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