Yes, the performance difference is significant. See the KB article “How to improve string concatenation performance in Visual C#”. I have always tried to code for clarity first, and then optimize for performance later. That’s much easier than doing it the other way around! However, having seen the enormous performance difference in my applications between … Read more
bool IsDigitsOnly(string str) { foreach (char c in str) { if (c < ‘0’ || c > ‘9’) return false; } return true; } Will probably be the fastest way to do it.
You can use this: SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp; This is much faster than: COUNT(DISTINCT column_name)
First make sure if the URL is actually valid (a string, not empty, good syntax), this is quick to check server side. For example, doing this first could save a lot of time: if(!$url || !is_string($url) || ! preg_match(‘/^http(s)?:\/\/[a-z0-9-]+(.[a-z0-9-]+)*(:[0-9]+)?(\/.*)?$/i’, $url)){ return false; } Make sure you only fetch the headers, not the body content: @curl_setopt($ch, … Read more
There isn’t much that’s special about C. That’s one of the reasons why it’s fast. Newer languages which have support for garbage collection, dynamic typing and other facilities which make it easier for the programmer to write programs. The catch is, there is additional processing overhead which will degrade the performance of the application. C … Read more
It’s not that i– is faster than i++. Actually, they’re both equally fast. What takes time in ascending loops is evaluating, for each i, the size of your array. In this loop: for(var i = array.length; i–;) You evaluate .length only once, when you declare i, whereas for this loop for(var i = 1; i … Read more
This is called finding the k-th order statistic. There’s a very simple randomized algorithm (called quickselect) taking O(n) average time, O(n^2) worst case time, and a pretty complicated non-randomized algorithm (called introselect) taking O(n) worst case time. There’s some info on Wikipedia, but it’s not very good. Everything you need is in these powerpoint slides. … Read more
On the one hand, throwing exceptions is inherently expensive, because the stack has to be unwound etc. On the other hand, accessing a value in a dictionary by its key is cheap, because it’s a fast, O(1) operation. BTW: The correct way to do this is to use TryGetValue obj item; if(!dict.TryGetValue(name, out item)) return … Read more
math.sqrt(x) is significantly faster than x**0.5. import math N = 1000000 %%timeit for i in range(N): z=i**.5 10 loops, best of 3: 156 ms per loop %%timeit for i in range(N): z=math.sqrt(i) 10 loops, best of 3: 91.1 ms per loop Using Python 3.6.9 (notebook).