Depth-first search (DFS) is an algorithm for traversing or searching Tree or Graph Data structures. The algorithm starts at the root node (selecting some arbitrary node as the root node in the case of a graph) and explores as far as possible along each branch before backtracking.

## Algorithm#

### Iterative#

procedure DepthFirstSearch (graph, rootNode) is
define a Stack: stack
define a Set: visited

stack.push(rootNode)

while not stack.empty() do
node = stack.pop()
if node not in visited then
if node is a goal then
return node
for connectedNode in graph.connectedNodes(node) do
stack.push(connectedNode)


Based on iterative algorithm in (“Depth-First Search” 2022). #+end_quote

### Recursive#

procedure DepthFirstSearch (graph, node) is
define a Set: visited

procedure DepthFirstSearchInner (graph, node) is
if node in visited then
return nil

if node is a goal then
return node

found = nil
for connectedNode in graph.connectedNodes(node) do
found = DepthFirstSearchInner(graph, connectedNode)
if found then
return found

return nil

return DepthFirstSearchInner(graph, node)


Based on recursive algorithm in (“Depth-First Search” 2022).

## References#

“Depth-First Search.” 2022. Wikipedia, June. https://en.wikipedia.org/w/index.php?title=Depth-first_search&oldid=1091833357.