README.md

1539. Kth Missing Positive Number

Given an array arr of positive integers sorted in a strictly increasing order, and an integer k.

Find the kth positive integer that is missing from this array.

Example 1:

Input: arr = [2,3,4,7,11], k = 5
Output: 9
Explanation: The missing positive integers are [1,5,6,8,9,10,12,13,...]. The 5th missing positive integer is 9.

Example 2:

Input: arr = [1,2,3,4], k = 2
Output: 6
Explanation: The missing positive integers are [5,6,7,...]. The 2nd missing positive integer is 6.

Constraints:

• 1 <= arr.length <= 1000
• 1 <= arr[i] <= 1000
• 1 <= k <= 1000
• arr[i] < arr[j] for 1 <= i < j <= arr.length

Solutions (Rust)

1. Solution

impl Solution {
    pub fn find_kth_positive(arr: Vec<i32>, k: i32) -> i32 {
        let mut k = k;
        let mut i = 0;

        for n in 1..2001 {
            if i >= arr.len() || n < arr[i] {
                k -= 1;
            } else {
                i += 1;
            }
            if k == 0 {
                return n;
            }
        }

        0
    }
}