# ---
# title: 41. First Missing Positive
# id: problem41
# author: Tian Jun
# date: 2020-10-31
# difficulty: Hard
# categories: Array
# link: <https://leetcode.com/problems/first-missing-positive/description/>
# hidden: true
# ---
# 
# Given an unsorted integer array `nums`, find the smallest missing positive
# integer.
# 
# **Follow up:**  Could you 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:**
# 
#   * `0 <= nums.length <= 300`
#   * `-231 <= nums[i] <= 231 - 1`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
