Postfix Evaluation
Push numbers; an operator pops two, applies itself, and pushes the result.
Decision · step 2 of 9Stacks for Expressions: Evaluate postfix
Push 2. The stack is now 2.
What you will see
Two values lift off, combine, and one drops back on.
Cost
| Best | O(n) |
|---|---|
| Average | O(n) |
| Worst | O(n) |
| Space | O(n) |
How you work with it here
play it through, step one change at a time, scrub to any step, run it on your own input, predict what happens next, try operations in any order.
Screen readers: Items announce position from the top or front and value; each step announces the operation and the new top or front.
Reduced motion: Items appear or disappear in place with a crossfade instead of sliding in or out.
Before this
Related
Taught by the same lesson
Stacks for Expressions covers these too, in the same run.