带宽拓展的E/F3类射频功率放大器设计(2020.09 MTT)–从理论到ADS版图 原文: A Generalized High-Efficiency Broadband Class-E/F3 Power Amplifier Based on Design Space Expanding of Load Network 发表于SEPTEMBER 2020，在微波顶刊IEEE T MTT上面，

降采样 在做降采样处理时，是先滤波，还是先降采样，二者有区别吗？ 在信号的处理过程中，对于同样地一段信号，先降采样再滤波和先滤波，再降采样，有区别吗？ 作者：AK23 链接：https://www.zhihu.com/question/23474073/answer/139260429 来源：知乎 首先抛出结论：先滤波，后抽取。原理很简单，上面已经有知友回答了，一句话就能概括，如果抽取时不先做

占坑

占坑

Problem Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST

Problem Find the sum of all left leaves in a given binary tree. Example Solution 首先就是我们只求叶子节点之和（左孩子右孩子为空就可以判断是否为叶子节点），然后需要判断是否是左边的叶子节点，所以我们只需要判断每个节点左边节点是否为空，如果不为空是否为叶子节点，如果成立我们就返回这个左孩子的值再加上向右边孩子

Problem Given a non-empty array of integers, return the k most frequent elements. Note: You may assume k is always valid, 1 ≤ k ≤ number of unique elements.Your algorithm’s time complexity must be

Problem The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, we get the following sequence for n = 3: “123” “132” “213” “231” “3