Algodle

Algodle trains the part of a coding interview that comes before the code: seeing which technique a problem needs.

Every day there's one original problem, the same for everyone. Read it, watch its examples acted out if you like, and pick the pattern you'd reach for, from 31 patterns such as two pointers, binary search, dynamic programming, and graph searches. Or say you're not sure. Then see why, in four parts:

• The Ask: the problem with its story stripped away, and the phrases the answer turns on. • The Tell: the words in the problem that give the technique away. • The Approach: a solution that has been run against its tests, with its steps to play through. • The Trap: the tempting wrong turn, and why each other option doesn't fit, or also works.

There's no code to type and nothing to keep up with. Every problem already shown stays in Past days, whenever you want another. Mix-ups shows the pairs of patterns you've mixed up on more than one problem, with how to tell them apart.

Today's problem is saved on your phone once it loads, so it opens without a connection, and so do the past days that came with the app.

No accounts and no tracking. Nothing about who you are, or what you pick, ever leaves your phone.

Every problem is original, written for Algodle, and every solution shown has been run against its tests.

Discovery signals