A valid parentheses string is either empty (""), "(" + A + ")", or A + B, where A and B are valid parentheses strings, and + represents string concatenation. For example, "", "()", "(())()", and "(()(()))" are all valid parentheses strings.

First, renew letsencrypt ssl certificate. And then copy the new SSL certificate files to zimbra's folder. Follow by replacing the existing commercial key with private key. Finally, deploy and then restart zimbra service.

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right. The first integer of each row is greater than the last integer of the previous row.

Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.

Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image.

Edit `Global.asax` file. Import the `System.Net` class and then change the security protocol to tls1.2 in the `Applicatin_Start` method.

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

Add the <meta charset="utf-8" /> tag inside the head tag of the web page. Also add the following setting inside the <configuration><system.web> tag in the web.config file.

Given an unsorted integer array, find the smallest missing positive integer.

Given a string, your task is to count how many palindromic substrings in this string.
The substrings with different start indexes or end indexes are counted as different substrings even they consist of same characters.

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Given a 32-bit signed integer, reverse digits of an integer.

Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length.
Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.
The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants.