[swift] LeetCode 234. Palindrome Linked List

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

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

func isPalindrome(_ head: ListNode?) -> Bool {
    var arr = Array(repeating: -1, count: 999999), p = head
    var i = 0, j = 0

    while let q = p {
        arr[i] = q.val
        p = q.next; i+=1
    }

    j = i-1; i = 0

    while i < j {
        if arr[i] != arr[j] { return false }
        i+=1; j -= 1
    }

    return true
}

func isPalindrome(_ head: ListNode?) -> Bool {

var arr = Array(repeating: -1, count: 999999), p = head

var i = 0, j = 0

while let q = p {

arr[i] = q.val

p = q.next; i+=1

}

j = i-1; i = 0

while i < j {

if arr[i] != arr[j] { return false }

i+=1; j -= 1

}

return true

}

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