Depth First Search algorithm with target node

Question

I have to use DFS algorithm for my university project. I saw this link DFS but i face this problem. The Depth First Search algorithm is Traversal it goes to every node in the graph but i want to define a target node when i reach to it i want to stop the algorithm i tried the following code but it still go to all node

void DFSUtil(int v, int goal, boolean visited[]) {
            visited[v] = true;

            Iterator<Integer> i = adj[v].listIterator();

            while (i.hasNext()) {
                int n = i.next();
                if (!visited[n]) {
                    if (n == goal) {
                        System.err.print(infoLinkedList.get(1).nameStation+":");
                        System.err.print(" |"+goal+ "| -> ");
                        return;
                    }
                }
            }
    }

In DFS, we need to visit all children of a node. This, in essence, means we need two loops: one for the termination condition, one to iterate over all children of the current node. Normally, we do this by adding a Dequeue<...> of work to do. If we read and write from the same side, we have a DFS algorithm. If we read form one side, but write to anoteher, we have BFS. I have a DFS implementation here if you want to take a look. — Turing85
– Turing85, Commented Jan 4, 2023 at 16:42
Also, if the target node is a final node of the graph or even absent at all, then all nodes will be traversed. — Boris Zhguchev
– Boris Zhguchev, Commented Jan 4, 2023 at 17:04

Pavel · Accepted Answer · 2023-01-04 16:51:39Z

2

Your algorithm is not DFS, it visits the neighbours of the node v and that's it. A DFS would look something like this:

void DFSUtil(int v, int goal, boolean visited[]) {
        Stack<Integer> stack = new Stack<>();
        stack.add(v);

        while (!stack.isEmpty()) {
            var n = stack.pop();
            if (!visited[n]) {
                if (n == goal) {
                    System.err.print(infoLinkedList.get(1).nameStation + ":");
                    System.err.print(" |" + goal + "| -> ");
                    return;
                }
                visited[n] = true;
                Iterator<Integer> i = adj[n].listIterator();
                while (i.hasNext()) {
                    stack.add(i.next());
                }
            }
        }
    }

answered Jan 4, 2023 at 16:51

Pavel

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