Computer science · a topic
Breadth-first and depth-first search, Taught not just answered.
A real-time, 1:1 lesson on Breadth-first and depth-first search: an AI teacher explains it out loud while it visualizes every step. Interrupt it, ask why, and it checks you got it, in 26 languages.
The idea
What is Breadth-first and depth-first search?
Breadth-first and depth-first search are the two basic ways of visiting every node in a graph or tree. Breadth-first search (BFS) explores level by level, visiting all neighbours of the start before moving outward, using a queue, which makes it find the shortest path in an unweighted graph. Depth-first search (DFS) follows one path as far as it can before backtracking, using a stack or recursion, which suits detecting cycles, ordering tasks and exploring mazes. Both mark visited nodes so they do not loop forever.
Where it appears: A Level Computer Science, AP CS A, university algorithms courses, GATE CS, coding interviews.
Where learners get stuck
Why Breadth-first and depth-first search is hard
Learners confuse which structure drives which search (queue for BFS, stack for DFS), forget to mark nodes visited and loop on cycles, and assume DFS finds shortest paths when only BFS does on unweighted graphs.
The picture a good explanation starts with: The same small graph drawn twice, with nodes numbered in BFS visiting order on the left and DFS order on the right, and the queue or stack contents shown at each step.
A lesson, step by step
How a lesson on Breadth-first and depth-first search goes
01
Ask
Type or say "When should I use BFS instead of DFS?" in your own words, in any of 26 languages.
02
Plan
The tutor plans a storyboard, one picture per idea, starting with the same small graph drawn twice, with nodes numbered in BFS visiting order on the left and DFS order on the right, and the queue or stack contents shown at each step.
03
Explain
It explains Breadth-first and depth-first search out loud while the picture builds step by step, pitched to your level (A Level Computer Science and up).
04
Interrupt
Say "wait, why?" or type a doubt: it stops, answers over the picture, and carries on. Ask for a different explanation any time.
05
Check
A checkpoint question makes sure the idea landed, and Tests keep the practice going.
06
Your notes
Upload a PDF or a photo of your class notes or a past paper and the lesson follows your textbook's terms.
Ask it anything
Questions learners ask about Breadth-first and depth-first search
- When should I use BFS instead of DFS?
- Why does BFS find the shortest path?
- How do I stop a graph search from looping forever?
Any of these, or your own, typed or spoken. The tutor answers on the picture and adapts to how well you are following.
Questions
Asked, Answered
Can LetMeTeach explain Breadth-first and depth-first search?
Yes. Ask in your own words and the tutor plans a lesson on Breadth-first and depth-first search: it starts with the same small graph drawn twice, with nodes numbered in BFS visiting order on the left and DFS order on the right, and the queue or stack contents shown at each step. Then it explains each step out loud as the picture builds, stops when you say "wait, why?", and ends with a checkpoint question.
Where does Breadth-first and depth-first search come up?
A Level Computer Science, AP CS A, university algorithms courses, GATE CS, coding interviews. The lesson is pitched to your level and the exam or curriculum you follow, and you can upload your own notes or past papers so it uses your textbook's terms.
Can I learn Breadth-first and depth-first search in my own language?
Yes. LetMeTeach teaches in 26 languages and plans the lesson in the language you choose rather than translating an English one, so the terms match what your textbook says. The Free plan includes 7 hours a month with no card.
Last updated
Learn Breadth-first and depth-first search, Starting now.
Ask "When should I use BFS instead of DFS?" and watch the answer drawn. The Free plan needs no card.