有信息/无信息搜索算法返回什么？是否返回目标节点的路径？

Great question—this is a foundational point in search algorithms, so let’s break it down with practical examples.

Uninformed Search Algorithms (Blind Search) #

Uninformed algorithms like BFS (Breadth-First Search), DFS (Depth-First Search), and UCS (Uniform-Cost Search) don’t use any additional "hint" information about the goal’s location. Here’s what they typically return:

• Core return value: First, they’ll confirm whether a goal node exists in the search space. If it does, the primary return is usually the goal node itself (with its state/attributes).
• Path inclusion: Almost all real-world implementations will also return the full path from the start node to the goal node. These algorithms track parent pointers for each node during traversal—once the goal is found, you can backtrack from the goal node through its parents to reconstruct the exact sequence of steps taken to reach it.
  • For example, BFS returns the shortest path (in terms of step count), UCS returns the lowest-cost path, and DFS returns any valid path (not necessarily optimal)—but all of these will give you the path unless you explicitly code the algorithm to only check for existence.

Informed Search Algorithms (Heuristic Search) #

Informed algorithms like A*, Greedy Best-First Search, and IDA* use heuristic functions (like estimated distance to the goal) to guide their search. Their return behavior is similar but optimized with the heuristic:

• Core return value: Again, they’ll first indicate if the goal is reachable. If yes, they return the goal node.
• Path inclusion: Just like uninformed searches, these algorithms almost always return the path to the goal. The heuristic helps them prioritize nodes that are more likely to lead to the goal quickly, but the end result needs to include the step-by-step path to be useful.
  • A*, for instance, guarantees the lowest-cost path (if the heuristic is admissible) and will return that optimal path. Greedy Best-First might return a suboptimal path but still provides the sequence of nodes taken to get there.

Edge Case: Minimal Implementations #

It’s worth noting that you could write a stripped-down version of any search algorithm that only returns a boolean (goal exists or not) or just the goal node without the path. But in most practical scenarios—whether you’re navigating a grid, solving a puzzle, or routing a robot—the whole point of the search is to find how to get to the goal, so returning the path is standard.

内容的提问来源于stack exchange，提问作者Joshua