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Given an unsorted integer array nums, find 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

class Solution { public int firstMissingPositive(int[] nums) { } }