package LeetCode_1539 /** * 1539. Kth Missing Positive Number * https://leetcode.com/problems/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. 1 <= arr.length <= 1000 2. 1 <= arr[i] <= 1000 3. 1 <= k <= 1000 4. arr[i] < arr[j] for 1 <= i < j <= arr.length * */ class Solution { /* * solution 1: Time:O(n), Space:O(1) * */ fun findKthPositive(arr: IntArray, k: Int): Int { val n = arr.size //because i start from 1, so nums[i] = i + 1, for (i in arr.indices) { //when the gap >= k, that is the missing kth number if (arr[i]-(i+1)>=k){ return k+i } } return n + k } }