How to Fix Linked List Palindrome Errors

In this tutorial, you'll learn about How to Fix Linked List Palindrome Errors. We cover key concepts, practical examples, and best practices.

Fix linked list palindrome errors when reversal modifies original list or comparison misses elements.

Quick Fix

Wrong

def pal(h):
    v=[]; c=h
    while c: v.append(c.val); c=c.next
    return v==v[::-1]

O(n) memory. Fails O(1) space constraint.

Right

def pal(h):
    s=f=h
    while f and f.next: s=s.next; f=f.next.next
    p=None
    while s: n=s.next; s.next=p; p=s; s=n
    l=h; r=p; ok=True
    while r:
        if l.val!=r.val: return False
        l=l.next; r=r.next
    return True

1->2->2->1 -> True. 1->2 -> False. O(n) time, O(1) space.

Prevention

Find middle, reverse second half, compare halves.

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