Description
Given an array arr
of positive integers sorted in a strictly increasing order, and an integer k
.
Return the kth
positive integer that is missing from this array.
Β
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 5thΒ 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.
Β
Constraints:
1 <= arr.length <= 1000
1 <= arr[i] <= 1000
1 <= k <= 1000
arr[i] < arr[j]
for1 <= i < j <= arr.length
Β
Follow up:
Could you solve this problem in less than O(n) complexity?
Solution
Python3
class Solution:
def findKthPositive(self, arr: List[int], k: int) -> int:
N = len(arr)
left, right = 0, N
def good(mid):
return arr[mid] - 1 - mid >= k
while left < right:
mid = left + (right - left) // 2
if good(mid):
right = mid
else:
left = mid + 1
return left + k