206. Reverse Linked List.js

// Given the head of a singly linked list, reverse the list, and return the reversed list.

// Example 1:

// Input: head = [1,2,3,4,5]
// Output: [5,4,3,2,1]
// Example 2:

// Input: head = [1,2]
// Output: [2,1]
// Example 3:

// Input: head = []
// Output: []

// Constraints:

// The number of nodes in the list is the range [0, 5000].
// -5000 <= Node.val <= 5000

// Follow up: A linked list can be reversed either iteratively or recursively. Could you implement both?

const reverseList = head => {
	let node = head
	let previous = null
	while (node) {
		let save = node.next
		node.next = previous
		previous = node
		node = save
	}
	return previous
}