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Understanding Depth First Search (DFS), With Examples

# Understanding Depth First Search (DFS), With Examples

## Key Points

• Depth-first search (DFS) is an efficient algorithm for traversing graphs or trees, exploring nodes as far as possible before returning and continuing down the next.
• DFS stacks previously visited nodes to avoid redoing work, ensuring an efficient process.
• Programmers use DFS to solve problems like finding connected parts of a network, finishing puzzles, or searching for elements in data structures.

When you’re trying to find specific information in a data tree, it’s helpful to have an algorithm that can quickly analyze nodes. One of the most effective tools for solving this problem is depth-first search, which runs through entire nodes while creating a stack.

DFS makes our programming lives easier, but how does it work? In this article, we break down the algorithm, exploring its methods and functions. We even provide an example syntax to get you started. So let’s start exploring nodes at length with DFS.

## How Does Depth First Search Work?

Have you wanted to find a particular element in a data structure? One effective algorithm for traversing graphs or trees is the depth-first search (DFS) module. This function explores a node as far as possible before returning and continuing down the next.

The DFS algorithm stacks its previously visited nodes, so it avoids redoing the work it’s already done. To ensure an efficient process, depth-first search follows a particular order:

1. Start at an arbitrary node or vertex.
2. Mark the node as visited.
3. Completely explore the current nodes and all unvisited adjacent nodes.
4. Mark all unvisited adjacent nodes as visited and add them to the stack.
5. Return to the origin and repeat steps 3 and 4 until the desired condition is met.

Depth-first search is particularly helpful for crawling binary search trees, where each node can only have two proceeding paths. This makes the algorithm fundamental in computer science. Let’s explore how it works.

## How Is the Algorithm Used in Programming?

Depth-first search effectively clears entire nodes of data from graphs and trees. Programmers can effectively use it to solve problems such as finding connected parts of a network, finishing puzzles, or searching for elements in a data structure. To use DFS in Python, review this example:

``````def dfs(graph, start, visited=None):
if visited is None:
visited = set()
print(start)  # Process the node here

for neighbor in graph[start]:
if neighbor not in visited:
dfs(graph, neighbor, visited)
``````

## Summary Table

What is depth-first search in programming?

Depth First Search (DFS) is a graph traversal algorithm used in programming to explore a graph or tree structure by visiting nodes in a depthward motion before backtracking. It starts at an arbitrary node, explores as far as possible along each branch before backtracking, and is commonly implemented using recursion or an explicit stack.

What is depth-first search used for?

Depth First Search (DFS) is used for various purposes in programming. It can be used to solve graph-related problems such as finding connected components, detecting cycles, or searching for paths in a graph. Additionally, DFS is often employed in maze-solving algorithms, puzzle-solving, and backtracking problems that involve exploring all possible solutions.

What is a graph traversal algorithm?

A graph traversal algorithm is a method used to systematically explore or visit all the vertices or nodes of a graph. It defines the order in which the nodes are visited and can be used to perform operations on the nodes, search for specific nodes or paths, or analyze the structure of the graph.

What is a binary data tree?

A binary data tree is a hierarchical data structure where each node can have at most two child nodes, commonly referred to as the left child and the right child.

#### Drew Baker, Author for History-Computer

Drew lives off-grid using a self-built solar array. He supports a nomadic lifestyle writing about solar energy, spaceflight, and anything travel-related. When he's not at the library, you'll typically find him chasing waterfalls despite all the warnings against it. You can connect with Drew on his Instagram.