1. Stack
DFS uses a stack to explore the most recent node first.
const stack = [start]Typorithm · medium
Depth-First Search
▷ Interactive algorithm labdepth-first-searchsearchgraphstacktraversal
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Full lesson · 8 learning steps Open any exercise for focused practice
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Step 1 of 8 · intro card
Learn Depth-First Search
Search Algorithms
Depth-First Search explores a graph by going deep along one path before backtracking.
DFS uses a stack to choose the most recently discovered node.
It can be implemented recursively or iteratively; this lesson uses a stack.
A visited set prevents cycles from causing repeated work.
DFS is useful for reachability, connected components, and backtracking-style exploration.
Preparing algorithm lab…
01
Use a stack.
02
Pop the newest node.
03
Skip already visited nodes.
04
Push neighbors to go deeper.
05
Time is O(V + E).
function depthFirstSearch(graph, start, target) {
const stack = [start];
const visited = new Set();
while (stack.length > 0) {
const node = stack.pop();
if (visited.has(node)) continue;
visited.add(node);
if (node === target) return true;
for (const neighbor of graph[node] ?? []) {
stack.push(neighbor);
}
}
return false;
}Read the implementation
Connect each part of the code to the concept before you type.
2. Visited set
visited prevents repeated processing.
const visited = new Set()3. Stack loop
Keep going while there are nodes to explore.
while (stack.length > 0)4. Pop node
Take the newest discovered node.
const node = stack.pop()5. Skip visited
Avoid processing a node twice.
if (visited.has(node)) continue6. Target check
Return true when DFS reaches the target.
if (node === target) return true7. Push neighbor
Neighbors are pushed for later depth-first exploration.
stack.push(neighbor)A complete learning loop
01
Understand
Read the concept map and follow the code breakdown.
02
Reconstruct
Type the implementation, repair mistakes and work through every recall exercise.
03
Verify
Use the final check without hints; revisit weak concepts in short practice sessions.