Linked ListEasyLeetCode #141

12. Detect Cycle / Loop ⭐

Floyd's algorithm moves slow by 1 and fast by 2. If a cycle exists, they are guaranteed to collide.

Time O(n) Space O(1)

Live loop — open the studio to scrub, add your own array, or race it in Battle Arena.

Asked in interviews at

AmazonMicrosoftBloomberg

Reference implementation (Python)

def has_cycle(head):
    slow = head
    fast = head
    while fast and fast.next:
        slow = slow.next
        fast = fast.next.next
        if slow == fast:
            return True
    return False

Embed this visualization

Drop a live, looping 12. Detect Cycle / Loop ⭐ canvas into a blog post or course page.

<iframe src="/embed/cycle-detection" 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 12. Detect Cycle / Loop ⭐?

12. Detect Cycle / Loop ⭐ runs in O(n) time and O(1) auxiliary space.

Is the 12. Detect Cycle / Loop ⭐ 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 12. Detect Cycle / Loop ⭐ in interviews?

12. Detect Cycle / Loop ⭐ shows up in interviews at Amazon, Microsoft, Bloomberg.

How does the 3D visualization of 12. Detect Cycle / Loop ⭐ 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.