22. Greedy

A greedy algorithm makes the best-looking choice at each step and never goes back. It's fast and simple, but it's only correct when you can argue that the local choice never blocks a better overall answer. If you can't make that argument, use dynamic programming.

The classic greedy choices: sort intervals by end time and keep the one that finishes first (activity selection); take the best value per unit first (fractional knapsack); track the furthest reach (jump game); reset the start when your running balance goes negative (gas station).