Greedy
Locally optimal choices that provably yield a global optimum.
Pick the maximum number of mutually compatible activities by repeatedly taking the one that finishes earliest.
The family of interval problems: unweighted selection (greedy by finish), interval partitioning into minimum rooms (greedy by start with a min-heap), and weighted selection (DP with binary search).
Maximize value in a capacity-limited knapsack when items can be taken in fractions: take items in decreasing value-per-weight order.
Build an optimal prefix-free binary code by repeatedly merging the two least frequent symbols with a min-heap.
Schedule unit-length jobs with deadlines and profits to maximize total profit: take jobs in profit order and place each in the latest free slot before its deadline.
Find the unique start on a circular route from which a car can complete the loop, in one pass: whenever the running tank goes negative, restart from the next station.
Sort intervals by start and sweep once, extending the current interval while the next one overlaps and emitting it when a gap appears.
Build a solution by repeatedly taking the locally best choice — correct only when an exchange argument proves that choice never hurts.