Summary of Depth First Search (DFS) with example | Uninformed Search | Artificial Intelligence

Summary of Video on Depth First Search (DFS)

Main Ideas and Concepts:

• Definition and Classification:
  • Depth First Search (DFS) is an uninformed search technique in artificial intelligence, similar to Breadth First Search (BFS).
  • Both algorithms operate without prior knowledge of the domain or goal state.
• Mechanism of DFS:
  • DFS uses a stack data structure (Last In First Out - LIFO) to explore nodes.
  • The algorithm goes deep into the graph or tree until it reaches a leaf node, then backtracks to explore other paths.
• Traversal Process:
  • Starting from a node (e.g., A), the algorithm can choose to explore child nodes (e.g., B and C) in any order.
  • The sequence of exploration can vary, but the underlying logic remains focused on reaching the deepest node first.
• Backtracking:
  • Once a leaf node is reached, the algorithm backtracks to the parent node to explore other unexplored paths.
• Characteristics of DFS:
  • Incomplete: DFS may not find a solution if the search space is infinite or if cycles exist, potentially leading to infinite loops.
  • Non-Optimal: DFS does not guarantee an optimal solution; it may find a solution that is more costly than another possible solution.
  • Time Complexity: The time complexity is generally O(V + E) (where V is the number of vertices and E is the number of edges) or O(b^d) in terms of branching factor (b) and depth (d).
• Comparison with BFS:
  • Unlike DFS, BFS is complete and will always find the shortest path if one exists, as it explores all nodes at the present depth before moving deeper.

Methodology/Instructions:

DFS Traversal Steps:

1. Start at the initial node and push it onto the stack.
2. While the stack is not empty:
   • Pop the top node from the stack.
   • If it is the goal node, return the path.
   • If not, push its unvisited children onto the stack.
3. If a node has no children, backtrack by popping the stack until a node with unvisited children is found.

Key Points:

• DFS operates on present knowledge without heuristic evaluations.
• It may lead to non-optimal solutions and can be incomplete in certain scenarios.

Speakers/Sources:

The video is presented by "Gate Smashers."

Notable Quotes

— 05:17 — « Incomplete means it is possible that it will not give me solution only. »

— 06:10 — « DFS is incomplete. Means what is incomplete? That I might not get solution and the DFS algorithm may get stuck into the loop. »

— 06:37 — « What is the concept of non optimal over here? BFS will always give optimal result only. »

— 07:10 — « Last point over here is time complexity. »

Category

Educational

Video