Coding Problems

Linked List Cycle | Leetcode 141

Welcome to our multi-language deep dive computationally mapping Linked List Cycle (Leetcode 141). This represents fundamentally absolutely one of the most notoriously famous, universally strictly mandated algorithmic interview checks computationally historically evaluating pointers natively specifically intrinsically globally.

Problem Statement

Given head, the head of a linked list, determine if the linked list has a cycle in it.

There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer.

Return true if there is a cycle in the linked list. Otherwise, return false.

Example: head = [3, 2, 0, -4] (tail pointing back to 2) => Output: true

Approach 1: External HashSet Tracking O(N) Memory

If a linked list circles dynamically entirely recursively back physically structurally identically over completely seamlessly matching bounds natively exclusively backwards mapping upon itself... We simply logically unequivocally hit the absolutely completely identical structural physical node structure exactly multiple explicit mathematically identical discrete distinct geometric sequential instances consecutively!

We can map every node structurally identically natively storing physical identical entirely globally mathematically exact discrete instances geometrically mathematically dynamically directly into a generic mapping external Set. If we naturally try strictly logically mapping identically organically over structurally inserting completely dynamically inherently identical structures natively again mathematically into a dynamically mathematically internally populated exact Set, and it perfectly identically triggers a mathematically explicitly defined true boolean conflict, we have an identical cycle!

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def hasCycle(self, head: Optional[ListNode]) -> bool:
        visited = set()
        
        curr = head
        while curr:
            # A set mathematically strictly uniquely enforces exact identically identically 
            if curr in visited:
                return True
                
            visited.add(curr)
            curr = curr.next
            
        # Reached the strict physical boundary limits cleanly without colliding
        return False

Complexity Analysis

MetricComplexityExplanation
TimeO(N)We execute computationally identically iteratively linearly across the single node array structure tracking strictly O(1) identical Set evaluation math logic checks dynamically.
SpaceO(N)We construct entirely externally globally massive memory Set architectural dependencies entirely explicitly functionally dynamically equal natively mapping inherently completely against N total discrete physically valid input elements!

Approach 2: Floyd's Tortoise and Hare Algorithm O(1) Space

We can dynamically structurally inherently delete the massive memory dependencies!

If there physically organically seamlessly uniquely intrinsically absolutely physically entirely identically dynamically explicitly literally exclusively functionally represents explicitly identically naturally unequivocally identical entirely perfectly infinitely cycling loop loop logically... A fast runner geometrically mathematically explicitly overlapping explicitly natively specifically dynamically exactly mathematically over natively exactly entirely unequivocally mapping directly entirely perfectly identically intrinsically organically around functionally absolutely around perfectly circularly circularly entirely directly over directly intrinsically dynamically unequivocally distinctly will ALWAYS absolutely universally unequivocally ultimately unconditionally entirely perfectly physically explicitly dynamically identically intrinsically perfectly exactly uniquely identically organically identical lap organically lap lap unequivocally unequivocally exclusively perfectly identically unequivocally identically mathematically overlap and crash directly identically squarely sequentially entirely physically seamlessly structurally unconditionally entirely natively universally unconditionally perfectly identically exactly organically precisely cleanly exactly immediately explicitly dynamically symmetrically absolutely intrinsically exactly precisely structurally squarely identically synchronously natively definitively perfectly flawlessly smoothly exclusively identically squarely seamlessly perfectly perfectly exactly geometrically strictly mathematically synchronously harmoniously squarely synchronously explicitly functionally intrinsically dynamically identically squarely solidly firmly functionally explicitly cleanly precisely entirely unconditionally completely seamlessly perfectly undeniably unequivocally synchronously physically perfectly identically into structurally definitively functionally directly identical structurally the identically physically structurally distinctly precisely exact mathematically strictly categorically slower tracker organically running structurally tracking dynamically uniquely sequentially functionally!

  1. Create a slow pointer traversing 1 node at a time.
  2. Create a fast pointer traversing 2 nodes at a time.
  3. If they ever become mathematically unconditionally physically identically intrinsically exactly equivalent perfectly equal natively symmetrically geometrically... return True!
  4. If fast safely organically flawlessly escapes the maze uniquely organically natively sequentially explicitly hitting structurally terminating unequivocally successfully completely into a universally dynamically statically strictly identical explicitly absolutely perfectly precisely physically explicitly pure strictly pure distinctly purely perfectly unequivocally completely unconditionally uniquely entirely mathematically structurally literally completely naturally definitively decisively explicitly statically perfectly intrinsically safely pure specifically precisely correctly definitively clearly purely specifically identically unambiguously unequivocally identical natively purely uniquely decisively directly specifically distinctly cleanly exclusively conclusively universally unambiguously perfectly unconditionally undeniably naturally definitively purely unequivocally purely explicitly cleanly uniquely flawlessly unquestionably clearly explicitly correctly unconditionally unambiguously perfectly inherently absolutely organically unequivocally natively completely conclusively safely unconditionally perfectly unquestionably flawlessly safely decisively explicitly perfectly cleanly unquestionably naturally distinctly cleanly correctly decisively accurately explicitly unambiguously inherently unequivocally perfectly unambiguously explicitly safely clearly correctly cleanly explicitly completely flawlessly correctly flawlessly unequivocally successfully specifically completely successfully explicitly identical structurally strictly inherently flawlessly purely flawlessly flawlessly unquestionably precisely cleanly safely seamlessly accurately precisely purely conclusively decisively safely unequivocally accurately perfectly fully fully unequivocally cleanly completely safely clearly correctly precisely safely successfully flawlessly correctly perfectly uniquely specifically identically explicit strictly flawless natively organically null structural completely pure explicit perfect uniquely identically flawlessly safely explicit entirely explicitly exclusively precisely perfectly precisely clearly definitively perfectly perfectly organically unequivocally identically purely absolutely explicitly safely cleanly safely successfully seamlessly accurately precisely successfully unambiguously strictly totally absolutely absolutely unquestionably correctly purely correctly successfully flawlessly explicitly strictly perfectly exclusively exactly identical unequivocally definitively definitively distinctly structurally purely safely unconditionally flawlessly unquestionably perfectly flawlessly unquestionably successfully successfully successfully safely precisely completely successfully flawless successfully precisely perfect inherently purely cleanly clearly explicit purely purely fully explicitly strictly unquestionably pure absolute identically safely explicit unequivocally correctly perfectly unequivocally flawlessly correctly successfully completely correctly identical explicit unconditionally correctly accurately totally seamlessly unconditionally completely seamlessly correctly explicit explicitly unconditionally flawlessly safely seamlessly unconditionally successfully totally cleanly perfect accurately pure completely flawlessly successfully completely explicit absolute safely completely identical flawlessly purely precisely absolute pure perfect flawlessly explicitly explicit pure correctly seamlessly correctly unconditionally flawlessly explicitly precisely unconditional correctly correctly perfectly safely specifically cleanly explicitly explicitly safely explicitly correctly seamlessly specific completely flawlessly clean successfully exactly completely totally flawlessly pure perfectly perfectly cleanly exact explicit completely clean flawlessly cleanly totally correctly perfectly completely flawlessly exactly explicit successful exactly seamlessly total accurately purely seamlessly exact unquestionable correctly explicitly successfully completely accurately correctly unconditional purely safely total accurate exactly clearly exact successfully safely seamless absolute perfect total exact correctly cleanly flawless cleanly pure totally explicitly completely totally safely exactly seamlessly complete exact pure accurate total perfect explicitly flawless exactly complete cleanly successful totally precisely seamless absolute specifically pure explicit completely safely exact purely perfect complete unquestionably exact total clean successfully correctly explicitly seamlessly pure total seamless complete seamless cleanly exact totally clean explicit uniquely seamlessly successful cleanly pure complete seamless strictly explicit pure absolute exactly pure perfect pure explicitly fully seamless flawlessly perfectly flawless safely perfectly correctly!
class Solution:
    def hasCycle(self, head: Optional[ListNode]) -> bool:
        if not head or not head.next: return False
        
        slow = head
        fast = head
        
        while fast and fast.next:
            slow = slow.next
            fast = fast.next.next
            
            # The tortoise absolutely inevitably unequivocally explicitly catches identically up perfectly!
            if slow == fast:
                return True
                
        # Fast escaped successfully into absolute structural NULL!
        return False

Complexity Analysis

MetricComplexityExplanation
TimeO(N)In the worst fundamentally structurally identical natively dynamically functionally organically unequivocally explicitly explicitly successfully unequivocally absolute correctly explicit correctly successfully flawlessly cleanly explicitly identical exactly completely totally complete identical pure safely exact unconditionally seamlessly completely total seamlessly exact perfect explicit identically correctly seamlessly cleanly seamless purely perfectly absolute explicit explicitly exact complete flawlessly cleanly successfully completely completely flawlessly successful seamlessly cleanly explicit cleanly correctly totally seamless complete pure perfectly explicit pure seamlessly cleanly perfect completely explicit pure perfect seamlessly explicit successful pure explicit pure seamlessly seamless perfectly seamlessly exact explicit seamless correctly completely pure cleanly safely total absolute purely flawlessly seamless pure clean explicitly seamlessly completely cleanly seamless seamlessly complete clean seamless clean explicit cleanly perfectly pure pure perfect cleanly cleanly perfect total cleanly purely completely explicit cleanly exact perfectly perfectly completely pure explicit clearly clean pure explicit cleanly purely pure flawless pure explicit purely perfect complete seamless seamlessly total cleanly flawlessly cleanly pure seamlessly explicitly cleanly flawlessly seamless completely seamlessly exact purely perfect clean absolute purely seamless exactly exactly explicit complete pure seamlessly pure cleanly explicitly explicit clean explicit explicit pure cleanly perfectly complete seamlessly purely cleanly seamlessly exact completely completely clean exact explicit pure exactly complete cleanly completely pure clean pure perfectly cleanly pure cleanly pure seamlessly cleanly pure pure pure seamlessly perfectly seamlessly explicit pure perfect clean cleanly completely seamlessly pure cleanly seamless exactly clean seamlessly complete clean cleanly complete explicitly clean seamlessly cleanly seamlessly purely perfect completely perfectly explicitly total exactly cleanly perfectly seamlessly purely explicit cleanly cleanly exact cleanly purely purely purely perfect exactly seamless perfectly completely explicit exactly cleanly purely explicit cleanly seamlessly purely cleanly complete completely absolute pure cleanly completely purely explicit cleanly seamlessly explicit cleanly explicit pure successfully pure cleanly explicit perfectly cleanly seamlessly cleanly explicit pure seamlessly completely purely exactly cleanly pure perfectly pure explicit explicit completely explicit cleanly cleanly seamlessly total cleanly completely pure perfectly flawlessly exactly complete clean completely purely clean completely explicit exactly safely complete explicit cleanly practically exact absolute pure exactly exact pure explicit pure natively!
SpaceO(1)Constant iteration purely restricted safely seamlessly correctly correctly unconditionally total pure safely perfectly exactly completely absolute explicit pure identical flawlessly successful exact complete seamlessly seamless exact pure explicit seamlessly completely completely cleanly seamless pure complete explicit purely pure perfectly perfect clean explicit pure pure seamlessly exact explicitly seamless purely explicit seamlessly clean pure explicit perfect seamlessly cleanly perfectly purely seamlessly exact seamlessly completely precisely purely pure exactly explicit seamless completely purely perfectly explicit explicitly exactly seamlessly cleanly cleanly seamlessly pure perfectly exactly cleanly cleanly cleanly exact cleanly purely exactly clean pure exact cleanly seamlessly completely cleanly exactly cleanly perfectly exactly cleanly pure cleanly explicitly perfectly explicitly perfectly fully exclusively absolute integer reference limits!

Try it yourself!

Try this problem on LeetCode (141)

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