234. Palindrome Chain List | Palindrome Linked List

Given a singly linked list, determine if it is a palindrome.

Example 1:

Input:1->2output:false

Example 2:

Input:1->2->2->1output:true

Follow up:
Could do it in O (n) time and O (1) space?

Please determine if a linked list is a palindrome list.

Example 1:

Input: 1->2 output: false

Example 2:

Input: 1->2->2->1 output: True

Advanced:
Can you solve this problem with O (n) time complexity and O (1) space complexity?

72ms

1 /**2 * Definition for singly-linked list.3 * public class ListNode {4 * public var val:int5 * public var next:listnode?6 * Public init (_ Val:int) {7 * Self.val = val8 * Self.next = nil9  *     }Ten  * } One  */ A classSolution { -Func Ispalindrome (_ Head:listnode?)Bool { -         varRoot =Head the         varstack =[ListNode] () -          whileRoot! =Nil { -Stack.append (root!) -root = root?. Next +         } -          +         varLow =0 A         varHigh = Stack.count-1 at          -          whileLow <High { -Let Lownode =Stack[low] -Let Highnode =Stack[high] -              -             ifLownode.val = =Highnode.val { inLow + =1 -High-=1 to}Else { +                 return false -             } the         } *         return true $     }Panax Notoginseng}

56ms

1 /**2 * Definition for singly-linked list.3 * public class ListNode {4 * public var val:int5 * public var next:listnode?6 * Public init (_ Val:int) {7 * Self.val = val8 * Self.next = nil9  *     }Ten  * } One  */ A classSolution { -Func Ispalindrome (_ Head:listnode?)Bool { -         varslow =Head the         varFast =Head -         varReverse:listnode? =Nil -          -          whileFast?. Next! =Nil { +Fast = fast!. next!. Next -Let next = slow!. Next +slow!. Next =Reverse AReverse =Slow atslow =Next -         } -         ifFast! =Nil { -slow = slow!. Next -         } -          in          whileSlow! =Nil { -             ifslow!. Val! = reverse!. val { to                 return false +             } -slow = slow!. Next theReverse = reverse!. Next *         } $         Panax Notoginseng         return true -     } the}

60ms

1 /**2 * Definition for singly-linked list.3 * public class ListNode {4 * public var val:int5 * public var next:listnode?6 * Public init (_ Val:int) {7 * Self.val = val8 * Self.next = nil9  *     }Ten  * } One  */ A classSolution { -Func Ispalindrome (_ Head:listnode?)Bool { -         varslow =Head the         varFast =Head -         varReverse: [INT] =[Int] () -Reverse.reservecapacity ( -) -          +          whileFast?. Next! =Nil { -Fast = fast!. next!. Next +Reverse.append (slow?. val)!) Aslow = slow?. Next at         } -         ifFast! =Nil { -slow = slow!. Next -         } -          -          whileSlow! =Nil { in             ifslow!. Val! =Reverse.poplast () { -                 return false to             } +slow = slow!. Next -         } the          *         return true $     }Panax Notoginseng}

234. Palindrome Chain List | Palindrome Linked List