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Implementation of Tree Traversal in java #149
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zsparal
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algorithm-archivists:master
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xam4lor:treetraversal-java
Jun 29, 2018
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02bd3c0
Added java examples for Tree Traversal
xam4lor 6f0aed8
Added java in mk file
xam4lor 3f919c6
Combined example and explanation code in one file
xam4lor 971a62f
Updated markdown file
xam4lor bc174f2
Added method overloading
xam4lor ff1c8de
Removed useless spaces
xam4lor c3aba0f
Updated Markdown file
xam4lor f6772a6
Updated code for coding conventions
xam4lor 8467c5f
Moved temp variable in bfsQueue()
xam4lor 374ee27
Update tree_traversal.md
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,18 @@ | ||
| //submitted by xam4lor | ||
| public class MainClass { | ||
| public static void main(String[] args) { | ||
| System.out.println("Creating Tree"); | ||
| Tree tree = new Tree(2, 3); | ||
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| System.out.println("Using recursive DFS :"); | ||
| tree.DFSRecursive(tree.root); | ||
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| System.out.println("Using stack-based DFS :"); | ||
| tree.DFSStack(); | ||
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| System.out.println("Using queue-based BFS :"); | ||
| tree.BFSQueue(); | ||
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| System.out.println(""); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,122 @@ | ||
| // submitted by xam4lor | ||
| import java.util.ArrayList; | ||
| import java.util.PriorityQueue; | ||
| import java.util.Queue; | ||
| import java.util.Stack; | ||
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| public class Tree { | ||
| // root node of the Tree | ||
| public Node root; | ||
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| public Tree(int numberRow, int numberChild) { | ||
| root = createTree(numberRow, numberChild); | ||
| } | ||
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| public void DFSRecursive(Node node) { | ||
| System.out.println(node.id); | ||
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| for (Node n : node.children) { | ||
| DFSRecursive(n); | ||
| } | ||
| } | ||
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| public void DFSRecursivePostOrder(Node node) { | ||
| for (Node n : node.children) { | ||
| DFSRecursivePostOrder(n); | ||
| } | ||
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| // Here we are doing something ... | ||
| System.out.println(node.id); | ||
| } | ||
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| // This assumes only 2 children | ||
| public void DFSRecursiveInOrderBTree(Node node) { | ||
| if(node.children.size() > 2) { | ||
| System.out.println("Not a binary tree!"); | ||
| System.exit(1); | ||
| } | ||
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| if(node.children.size() > 0) { | ||
| DFSRecursiveInOrderBTree(node.children.get(0)); | ||
| System.out.println(node.id); | ||
| DFSRecursiveInOrderBTree(node.children.get(1)); | ||
| } | ||
| else { | ||
| System.out.println(node.id); | ||
| } | ||
| } | ||
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| public void DFSStack() { | ||
| Stack<Node> stack = new Stack<Node>(); | ||
| stack.push(this.root); | ||
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| Node tmp; | ||
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| while(stack.size() != 0) { | ||
| System.out.println(stack.peek().id); | ||
| tmp = stack.pop(); | ||
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| for (Node c : tmp.children) { | ||
| stack.push(c); | ||
| } | ||
| } | ||
| } | ||
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| public void BFSQueue() { | ||
| Queue<Node> queue = new PriorityQueue<Node>(); | ||
| queue.add(this.root); | ||
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| Node temp; | ||
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| while(queue.size() != 0) { | ||
| System.out.println(queue.peek().id); | ||
| temp = queue.poll(); // return null if the queue is empty | ||
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| if(temp != null) { | ||
| for (Node c : temp.children) { | ||
| queue.add(c); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| public Node createTree(int numberRow, int numberChild) { | ||
| Node ret = new Node(numberRow); | ||
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| if(numberRow == 0) { | ||
| return ret; | ||
| } | ||
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| for (int i = 1; i < numberChild; i++) { | ||
| Node child = createTree(numberRow - 1, numberChild); | ||
| ret.children.add(child); | ||
| } | ||
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| return ret; | ||
| } | ||
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| private class Node implements Comparable<Node> { | ||
| public ArrayList<Node> children; | ||
| public int id; | ||
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| public Node(int id) { | ||
| this.children = new ArrayList<Node>(); | ||
| this.id = id; | ||
| } | ||
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| @Override | ||
| public int compareTo(Node other) { | ||
| // Need to implement Comparable<Node> and override this | ||
| // method because of the method BFSQueue() which uses Queues | ||
| // and must know how to check if two nodes are the same or not | ||
| return Integer.compare(this.id, other.id); | ||
| } | ||
| } | ||
| } | ||
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You should really just remove these versions. They are not any more clear and they take up a bunch of space for no reason. People who'll want to use the Java implementation will know what
this.rootmeans in the other implementations.There was a problem hiding this comment.
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But we need this method to have a parameter of type Node.
I have two solutions : one is to create a function with a same name but no parameters like DFSRecursive() who just call DFSRecursive(this.root).
Or I call DFSRecursive(null) and check if the node is null, the node equals this.root.
In java we cannot create functions within other functions.
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You could create a private function under the public one which does the recursive part and then you can include both in the code example
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I was about to suggest method overloading as well. Is there a reason not to?
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It was one of my solutions, I think It's the better thing to do. (overloading)