Like stacks, queues allow for the ordering of objects while following a certain set of rules. Nobody can cut in front of you, and you are guaranteed to get out from the front of the line (dequeue) before anybody behind you.
When you get in line (or enqueue) for an amusement park ride, you have your spot in line. Click on a brick to push it onto the stack in the correct order. Here is a visualization of a stack of numbered bricks, written by Dartmouth student Daniel Shanker. We say that the stack is “last in, first out” for this reason. In order to access the bottom plate of a stack of heavy plates, you might first have to take off all of the plates above it one by one, starting from the top. When you take an object off of the stack, it’s taken off the top of the stack. When you add an object to the stack, it’s added to the top of the stack. StacksĪ stack data structure models a familiar way of organizing objects in the physical world: stacked objects. We’ll look at stacks, queues, and dictionaries. Sometimes data structures are used to organize important data (for example, a collection of names and associated phone numbers), and sometimes data structures are used for book-keeping as an algorithm runs. If you were solving a Sudoku puzzle, you would mark down some possible numbers in each cell.Ī data structure allows information to be organized and stored. For example, if you had to find a path through a picture of a maze, you might use your pencil to draw some paths as you worked out the problem. Sometimes when you solve a problem, it’s helpful to take some notes as you go: book-keeeping.
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