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README.md

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Given an unsorted integer array nums, return the smallest missing positive integer.

You must implement an algorithm that runs in O(n) time and uses constant extra space.

 

Example 1:

Input: nums = [1,2,0]
Output: 3

Example 2:

Input: nums = [3,4,-1,1]
Output: 2

Example 3:

Input: nums = [7,8,9,11,12]
Output: 1

 

Constraints:

  • 1 <= nums.length <= 5 * 105
  • -231 <= nums[i] <= 231 - 1

Related Topics

[Array] [Hash Table]

Similar Questions

  1. Missing Number (Easy)
  2. Find the Duplicate Number (Medium)
  3. Find All Numbers Disappeared in an Array (Easy)
  4. Couples Holding Hands (Hard)

Hints

Hint 1 Think about how you would solve the problem in non-constant space. Can you apply that logic to the existing space?
Hint 2 We don't care about duplicates or non-positive integers
Hint 3 Remember that O(2n) = O(n)