1+ '''
2+ The DFS algorithm is a recursive algorithm that uses the idea of backtracking. It involves exhaustive searches of all
3+ the nodes by going ahead, if possible, else by backtracking.
4+ Here, the word backtrack means that when you are moving forward and there are no more nodes along the current path,
5+ you move backwards on the same path to find nodes to traverse. All the nodes will be visited on the current path
6+ till all the unvisited nodes have been traversed after which the next path will be selected.
7+ This recursive nature of DFS can be implemented using stacks. The basic idea is as follows:
8+ Pick a starting node and push all its adjacent nodes into a stack.
9+ Pop a node from stack to select the next node to visit and push all its adjacent nodes into a stack.
10+ Repeat this process until the stack is empty. However, ensure that the nodes that are visited are marked.
11+ This will prevent you from visiting the same node more than once. If you do not mark the nodes that are visited
12+ and you visit the same node more than once, you may end up in an infinite loop.
13+
14+ Time Complexity: O(V + E)
15+ Space Complexity: O(V)
16+ V is number of vertices (nodes), E is number of edges
17+ '''
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