Smallest Positive Missing Number
Places elements at their correct indexed bucket nums[i] == i + 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(arr):
n = len(arr)
for i in range(n):
while 1 <= arr[i] <= n and arr[arr[i]-1] != arr[i]:
arr[arr[i]-1], arr[i] = arr[i], arr[arr[i]-1]
for i in range(n):
if arr[i] != i + 1: return i + 1
return n + 1Embed this visualization
Drop a live, looping Smallest Positive Missing Number canvas into a blog post or course page.
<iframe src="/embed/smallest-positive-missing" 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 Smallest Positive Missing Number?
Smallest Positive Missing Number runs in O(n) time and O(1) auxiliary space.
Is the Smallest Positive Missing Number 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 Smallest Positive Missing Number in interviews?
Smallest Positive Missing Number shows up in interviews at Uber, Microsoft, DoorDash.
How does the 3D visualization of Smallest Positive Missing Number 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.