题目介绍

Given a linked list, remove the n-th node from the end of list and return its head.

Example:

1

Given linked list: 1->2->3->4->5, and n = 2.

2

3

After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:

Given n will always be valid.

Follow up:

Could you do this in one pass?

题目介绍

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.

A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

简介

强化学习的两大特点：

• 试错搜索：强化学习过程中不会有label反馈给模型，而是让模型学习哪种action可以获得最大的reward。
• 延迟奖励：大部分情况下，当前的action不但会影响此刻返回的reward，还会影响接下来序列的reward.