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) return head;
    let vir = new ListNode(-1);
    reverse(head, head.next, vir);
    head.next = null;
    return vir.next;
}
function reverse(node, pre, vir) {
    if(pre != null) {
        reverse(pre, pre.next, vir);
        pre.next = node;
    } else {
        vir.next = node;
    }
}
module.exports = {
    ReverseList : ReverseList
};