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Solution: First Missing Positive

Discover how to identify the smallest missing positive integer in an unsorted array by applying an in-place cyclic sort algorithm. Learn to efficiently reorder elements, ignore negatives, and achieve an O(n) time complexity with O(1) space, enhancing your coding interview problem-solving skills.

Statement

Given an unsorted integer array, nums, return the smallest missing positive integer. Create an algorithm that runs with an O(n)O(n) time complexity and utilizes a constant amount of space.

Note: The smallest missing positive isn’t the first positive number that’s missing in the range of elements in the input, but the first positive number that’s missing if we start from 11.

Constraints:

  • 11 \leq nums.length 105\leq 10^5

  • 231-2^{31} \leq ...