| 232用栈实现队列 |
https://leetcode.cn/problems/implement-queue-using-stacks/ |
| 225用队列实现栈 |
https://leetcode.cn/problems/implement-stack-using-queues/ |
| 20有效的括号 |
https://leetcode.cn/problems/valid-parentheses/ |
| 1047删除字符串中的所有相邻重复项 |
https://leetcode.cn/problems/remove-all-adjacent-duplicates-in-string/ |
| 150逆波兰表达式求值 |
https://leetcode.cn/problems/evaluate-reverse-polish-notation/ |
| 239滑动窗口最大值 |
https://leetcode.cn/problems/sliding-window-maximum/ |
| 347前K个高频元素 |
https://leetcode.cn/problems/top-k-frequent-elements/ |
| 692.前K个高频单词 |
https://leetcode.cn/problems/top-k-frequent-words/ |
| 42.接雨水 |
https://leetcode.cn/problems/trapping-rain-water/ |