class Solution func firstMissingPositive_ nums Int - Int var nums = nums var n Int = numscount for i in 0n while numsi 0 && numsi = n && numsnumsi - 1 != numsi

class Solution: def firstMissingPositive(self, nums: List[int]) -> int: n = len(nums) for i in range(n): while nums[i] > 0 and nums[i] <= n and nums[nums[i] - 1] != nums[i]: nums[nums[i] - 1], nums[i] = nums[i], nums[nums[i] - 1]

    for i in range(n):
        if nums[i] != i + 1:
            return i + 1
    
    return n + 1