leetcode-206-反转链表

leetcode原题

解题方法一

var reverseList = function(head) {
    let prev = null
    let current = head
    while (current) {
        const next = current.next
        current.next = prev
        prev = current
        current = next
    }
    return prev
}

解题方法二

var reverseList = function(head) {
    let newHead = null

    for (let i = head; i !== null; i = i.next) {
        newHead = new ListNode(i.val, newHead)
    }
    return newHead
};