题解 | #反转链表#

/*class ListNode {
 *     val: number
 *     next: ListNode | null
 *     constructor(val?: number, next?: ListNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.next = (next===undefined ? null : next)
 *     }
 * }
 */
/**
 * 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
 */
export function ReverseList(head: ListNode): ListNode {
    // write code here
    if(head == null || head.next == null) return head
    let newList = head
    let nextNode = head.next
    head.next = null
    while(nextNode) {
        const temp = nextNode.next
        nextNode.next = newList
        newList = nextNode
        nextNode = temp
    }
    return newList
}