题解 | #反转链表#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 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
     */
    public ListNode ReverseList (ListNode head) {
        // write code here
        ListNode prev = null;
        ListNode curr = head;
        ListNode tempNext = null;

        while( curr != null) {
            tempNext = curr.next;
            curr.next = prev;
            prev = curr;
            curr = tempNext;
        }

        ListNode newHead = prev;
        return newHead;

    }
}