0876 Middle of the Linked List

Solved at: 2023-01-29

Question

Solution

swift

class Solution {    func middleNode(_ head: ListNode?) -> ListNode? {        print("start")        var count = 0        var headcopy = head
        while(headcopy != nil) {            headcopy = headcopy!.next            count += 1        }
        var fin = count / 2
        headcopy = head
        for _ in 0..<fin {            headcopy = headcopy!.next        }
        return (headcopy)    }}

class Solution {    func middleNode(_ head: ListNode?) -> ListNode? {        print("start")        var count = 0        var headcopy = head
        while(headcopy != nil) {            headcopy = headcopy!.next            count += 1        }
        var fin = count / 2
        headcopy = head
        for _ in 0..<fin {            headcopy = headcopy!.next        }
        return (headcopy)    }}

Results

Runtime 3 ms Beats 84.39%
Memory 14.4 MB, Beats 13.82%

Complexity Analysis

$O(N)$
$O(1)$

Improved

swift

class Solution {    func middleNode(_ head: ListNode?) -> ListNode? {        var fast = head        var slow = head        while (fast != nil && fast!.next != nil) {            fast = fast!.next!.next            slow = slow!.next        }        return slow    }}

class Solution {    func middleNode(_ head: ListNode?) -> ListNode? {        var fast = head        var slow = head        while (fast != nil && fast!.next != nil) {            fast = fast!.next!.next            slow = slow!.next        }        return slow    }}

Runtime 6 ms Beats 54.85%
Memory 14 MB, Beats 70.57%