First Missing Positive

arrayhash table

Given an unsorted integer array nums . Return the smallest positive integer that is not present in nums .

You must implement an algorithm that runs in O(n) time and uses O(1) auxiliary space.

Example 1

Input: nums = [1,2,0]
Output: 3
The numbers in the range [1,2] are all in the array.

Example 2

Input: nums = [3,4,-1,1]
Output: 2
1 is in the array but 2 is missing.

Example 3

Input: nums = [7,8,9,11,12]
Output: 1
The smallest positive integer 1 is missing.

1 <= nums.length <= 10 ^5

-2 ^31 <= nums[i] <= 2 ^31 - 1

😤

Hard

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicHash Table