LeetCode75-206-Reverse-Linked-List

🧠 思路总结

把每个节点的 next 指向它前一个节点。

原来： 1 → 2 → 3 → 4 → 5 → null
变成： 5 → 4 → 3 → 2 → 1 → null

✅ 代码（Java）

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode pre = null;
        ListNode curr = head;
        while (curr != null) {
            ListNode next = curr.next;
            curr.next = pre;
            pre = curr;
            curr = next;
        }
        return pre;
    }
}