First Missing Positive Integer
Bucket sort in-place places each value x at index x - 1.
Live loop — open the studio to scrub, add your own array, or race it in Battle Arena.
Asked in interviews at
Reference implementation (Python)
def first_missing_positive(nums):
n = len(nums)
for i in range(n):
while 1 <= nums[i] <= n and nums[nums[i]-1] != nums[i]:
p = nums[i] - 1
nums[i], nums[p] = nums[p], nums[i]
for i in range(n):
if nums[i] != i + 1: return i + 1
return n + 1Embed this visualization
Drop a live, looping First Missing Positive Integer canvas into a blog post or course page.
<iframe src="/embed/first-missing-positive" width="100%" height="380" style="border:1px solid #e6e8ec;border-radius:14px" loading="lazy" title="3D algorithm visualization by CodeWithMunnaX"></iframe>Frequently asked
What is the time and space complexity of First Missing Positive Integer?
First Missing Positive Integer runs in O(n) time and O(1) auxiliary space.
Is the First Missing Positive Integer visualizer free?
The core 3D visualizer, Web Audio chimes and step intuition are free. A one-time ₹49 Pro Pass unlocks advanced algorithms, large custom arrays, Battle Arena and reel export.
Which companies ask First Missing Positive Integer in interviews?
First Missing Positive Integer shows up in interviews at Atlassian, Shopify, LinkedIn.
How does the 3D visualization of First Missing Positive Integer work?
Each array value becomes a 3D pillar whose height maps to its value. Comparisons glow amber, swaps flash red, and settled elements lock green while a floating pointer badge tracks the active index — synchronized line-by-line with the Python code.