题解 | 反转链表

/*
 * function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @return ListNode类
 */
function ReverseList( head ) {
    // write code here
 if(head==null||head.next==null){
    return head
 }
 let prev=null
 let curr=head
 while(curr){
    //先存下一个，再反转，再移动指针
   let next=curr.next
    curr.next=prev
    prev=curr
    curr=next

 }
 return prev
    
}
module.exports = {
    ReverseList : ReverseList
};