q041_first_missing_positive

Overview ¶

[Hard] First Missing Positive https://leetcode.com/problems/first-missing-positive/

Given an unsorted integer array, find the smallest missing positive integer.

Example 1:

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

Example 2:

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

Example 3:

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

Follow up:

Your algorithm should run in O(n) time and uses constant extra space.