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 last = null;

        while(head!=null){
            ListNode next = head.next;
            head.next = last;
            last = head;
            head = next;
        }
        
        return last;
    }
}

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