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Questions tagged [depth-first-search]

Depth-first search (DFS) is an algorithm for traversing or searching a tree, tree structure, or graph. One starts at the root (selecting some node as the root in the graph case) and explores as far as possible along each branch before backtracking.

Depth-first search (DFS) is an algorithm for traversing or searching a tree, tree structure, or graph. One starts at the root (selecting some node as the root in the graph case) and explores as far as possible along each branch before backtracking.

Formally, DFS is an uninformed search that progresses by expanding the first child node of the search tree that appears and thus going deeper and deeper until a goal node is found, or until it hits a node that has no children. Then the search backtracks, returning to the most recent node it hasn't finished exploring. In a non-recursive implementation, all freshly expanded nodes are added to a stack for exploration.

Source.

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non recursive dfs (when to mark it visited?)

So I recently implemented a non-recursive version of DFS. Turns out that I can mark the nodes "visited" as soon as they are pushed on the stack or when they are popped out. The problem which I was working on specifically stated to mark it "visited"…
ishan3243
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DFS algorithm in Python with generators

Background: I was working on a project were I needed to write some rules for text processing. After working on this project for a couple of days and implementing some rules, I realized I needed to determine the order of the rules. No problems, we…
oz123
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DFS on undirected graph complexity

Let's say I have an undirected graph with V nodes and E edges.If I represent the graph with adjacency lists,if I have a representation of an edge between x and y,I must also have a representation of the edge between y and x in the adjacency list. I…
Emil Grigore
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Ideal algorithm for finding all paths in a graph

Let's take this graph for example: Now let's say I'm starting at vertex 3 and want to find vertex 7. Depth first search (depending on the implementation) will look at the children first. Now, in our example, for the sake of the argument, I start…
None None
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finding all vertices that are a part of a simple cycle

Is there a way to find all vertices that are a part of a simple cycle in a graph in a linear time? I found a way to do it in O(|V|(|V|+|E|)) time but was wondering if there is a way to do it faster?
Amnon
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Why is my logic not working correctly for SPOJ TOPOSORT?

The given problem is http://www.spoj.com/problems/TOPOSORT/ The output format is particularly important as : Print "Sandro fails." if Sandro cannot complete all his duties on the list. If there is a solution print the correct ordering, the jobs to…
Kavish Dwivedi
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Why use DFS to find cycles in an undirected graph and topological sorting to find cycles in a directed graph?

For undirected graphs , if we need to find a cycle , we use depth-first search as described in this older question,which is a well known method and also optimal . But for directed graph, this other question suggests using topological sorting. My…
Spandan
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Performing DFS and BFS on a directed graph

Suppose we have a graph such as: If you wanted a path from 0 to 5, in what order will we visit the nodes if we perform DFS and BFS on this graph (assume the lowest element is always pushed first). I'm having trouble conceptualizing how the…
Bob John
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Closest pair of points algorithm variation

I know this may be a duplicate, but it seems like a variation on the 'Closest pair of Points' algorithm. Given a Set of N points (x, y) in the unit square and a distance d, find all pair of points such that the distance between them is at most…
Fernando
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How to find longest path in graph?

We are given an Adjacency list of the form U -> (U,V,C) -> (U,V,C) ... U2 -> ... U3 -> ... . . etc (U,V,C) means there's an edge from U to V with cost C. The given Adjacency list is for a single connected tree with N nodes thus containing…
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DFS Algorithm Traversal

Given the above graph, the DFS traversal with a stack gives me the folowing path... 1-2-3-4-5-6 Is the above path valid? Does there exists another path? (my textbook gives me 1-2-3-6-4-5) I don't have enough rep to post images over at computer…
user1234440
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Maintaining iterator in Boost::graph while performing DFS

Most of the examples for the Boost:graph library perform depth-first-search by calling boost's depth first search utilities. After creation of the vertices and edges, calling DFS on the graph traverses the entire graph in a depth-first manner and if…
sc_ray
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Why is BFS better suited to parallelization than DFS?

I've read that the BFS algorithm is better suited to parallel implementation than DFS. I'm having trouble grasping the intuition of why this should be true. Can anyone explain? Thanks
azphare
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graph - How to avoid reprocessing same edge twice in Depth First Search?

The Algorithm Design Manual describes BFS and DFS quite well. The code for dfs in the book has a problem when deciding whether or not to avoid double processing edges. I found the Errata and applied the errata to the code, but still I think the…
Jackson Tale
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DFS: How to indicate the nodes of the connected components in C++

I am making a problem of ACM competitions to determine the number of connected components that have an undirected graph G and vertices belonging to each component. 've Already done with a DFS algorithm, counting the number of connected components of…
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