单向链表翻转

revert_list.js

/*
head: 
{
  val: xx,
  next: xx
 }
 tail: 
 {
  val:xx,
  next: null
 }
*/
function revertList(head)
{
    // write code here
    var last = null
    var node = head
    while (node) {
        let tmp = node.next
        head.next = last
        last = node
        node = tmp
    }
    return last
}