I made a careless mistake in the code, thanks for pointing it out. So we detect cycle in graph and return true. ![]() If it is already in the recursion stack, this means we are going to repeat the recursion call which results in a cycle. However, this isn't a typical DFS, cause the list it's trying to traverse is different every time, also, the first item should always be added to path no matter what. dfs (graph, node, visited, recursionStack) Inside the dfs function, check if the node is already in the recursion stack. Then use DFS to search for the list of target strings.Įvery time it searches the current item and also all the items in idList, if a match is found add this item to path, until it finds all string in targets. If no adjacent vertex is found, pop up a vertex from the stack. But we want to have a stream of nodes, not a stream of list of nodes. Following is how a DFS works Visit the adjacent unvisited vertex. For example, in the following graph, we start traversal from vertex 2. To avoid processing a node more than once, we use a boolean visited array. The only catch here is, unlike trees, graphs may contain cycles, so we may come to the same node again. Since the database could be very large, I store all the variable as in HashMap as a class variable. A stack (often the program's call stack via recursion) is generally used when implementing the algorithm. Depth First Traversal (or Search) for a graph is similar to Depth First Traversal of a tree. Here is how I try to address this problem. Since DFS has a recursive nature, it can be implemented using a stack. Every time we try to access an item through id, we need to make sure this id is valid.įor the example given above, one possible path is, ,, , ].Īnother example, Given a start id "Sarah", and target string set we are trying to collect is, one possible path is, ]. ![]() ![]() Extra memory, usually a stack, is needed to keep track of the nodes. Given a start id “Donald”, and target string set we are trying to collect is, list all possible ways to visit all strings in target set. Depth-first search (DFS) is an algorithm for traversing or searching tree or graph data. Id, a list of id it has access to(can be empty), string(can be empty) We have a self-defined data structure have the following attributes:
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