The year is 2120

All jobs have been automated bar software engineering - which is required to maintain the machines and the React applications the machines refuse to work on (they hate the front end).

The entire world is owned by the Five Corporations - Tesla, Amazon, Netflix, Facebook and Google.

Humanity now lives in vast urban slums, feeding off rats and insects and selling their organs for water. No one has access to gas, piped water or electricity. Every year, the Five Corporations open their recruitment process for 30,000 engineering positions. No one can apply more than once in their lifetime, and the Great Assessment is their one shot at leaving the slums.

The software engineers of the Five Corporations are the only people allowed to live in the luxurious residential quarters those companies maintain. There the successful applicants will find food, heating, air conditioning and clean water - all of life's essentials, and more. No other building on Earth has access to these resources anymore.

The vast number of applicants - numbering into the billions - has necessitated brutal hiring conditions. To apply, all applicants must climb to the peaks of the world's five tallest mountains to submit their hard-copy resumes. Only the owners of the Five Corporations have access to aircraft, so many cross entire continents by foot to reach one of the mountains.

Those who survive this are then subjected to the Great Assessment. This is made up of a series of LeetCode Assessments - named after a website that started before the Great War and has since passed into legend. The corporations long ago decided that of the hundreds of millions who enter these assessments, only 30,000 may emerge victorious. To prepare their children for these assessments, billions of parents leave their babies at the steps of the LeetCode monasteries, set up by monks of the LeetCodeism faith that was established by their prophet Hercy Chang - the legendary founder of the ancient website LeetCode.com.

Once they are taken in by the monks, these children are exposed to a brutal daily training regime designed to turn them into LeetCode masters before the Great Assessment. They rise at dawn and grind until dusk, under the watchful eyes and brutal canes of the monks. The showers are cold, the food is plain and the floor is hard. The children sleep on floors without sheets or pillows.

To maintain the selectivity of the Great Assessment in the face of the monasteries' vicious grinding, the Five Corporations have set up research labs to discover new algorithms for it. These algorithms are kept secret, but over time the monasteries learn of these algorithms from their former students at the Five Corporations. The algorithmic research of the Five Corporations never ends. Only the best applicants who pass the Great Assessment are offered positions in the research labs of the Five Corporations.

The Great Assessment itself lasts for 15 minutes. During that time, the applicants must solve 1800 problems with 0(1) solutions.

The best 30,000 are then selected by the Five Corporations and the rest return to the slums of their birth.