Contest or problem URL. Each problem becomes a tab with its samples and time limit.
AtCoderCodeChefCodeforces → Bookmarklet
Works on Codeforces, AtCoder, CodeChef and most judges — nothing to
install, and it works during live contests. Drag this button to your bookmarks bar. On any
problem or contest page, click it — the problems land here with their samples.
Select the whole problem page (Ctrl+A, Ctrl+C) and paste it here.
Stress testing
Your editor code is the main solution ().
It runs against a slow-but-correct brute force on random tests from the generator until their outputs differ.
My snippets
Type the prefix in the editor and accept the suggestion to expand the body.
Tabstops: $1, $2… jump with Tab, ${1:name} pre-fills a default,
the same $1 in several places edits them together, $0 is where the cursor ends.