LeetCode-in-Java

1673. Find the Most Competitive Subsequence

Medium

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

Solution

public class Solution {
    public int[] mostCompetitive(int[] nums, int k) {
        int[] r = new int[k];
        int n = nums.length;
        int j = 0;
        for (int i = 0; i < n; i++) {
            if (i == 0) {
                r[j] = nums[i];
                j++;
            } else {
                int l = j - 1;
                while ((l >= 0) && (nums[i] < r[l]) && ((n - i) >= (k - l))) {
                    l--;
                }
                j = l + 1;
                if (j < k) {
                    r[j] = nums[i];
                    j++;
                }
            }
        }
        return r;
    }
}

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