105 lines
2.3 KiB
Java
105 lines
2.3 KiB
Java
package DataStructures.Trees; // Java program to print top view of Binary tree
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import java.util.HashSet;
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import java.util.LinkedList;
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import java.util.Queue;
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// Class for a tree node
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class TreeNode {
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// Members
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int key;
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TreeNode left, right;
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// Constructor
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public TreeNode(int key) {
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this.key = key;
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left = right = null;
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}
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}
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// A class to represent a queue item. The queue is used to do Level
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// order traversal. Every Queue item contains node and horizontal
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// distance of node from root
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class QItem {
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TreeNode node;
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int hd;
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public QItem(TreeNode n, int h) {
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node = n;
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hd = h;
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}
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}
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// Class for a Binary Tree
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class Tree {
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TreeNode root;
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// Constructors
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public Tree() {
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root = null;
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}
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public Tree(TreeNode n) {
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root = n;
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}
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// This method prints nodes in top view of binary tree
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public void printTopView() {
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// base case
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if (root == null) {
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return;
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}
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// Creates an empty hashset
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HashSet<Integer> set = new HashSet<>();
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// Create a queue and add root to it
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Queue<QItem> Q = new LinkedList<QItem>();
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Q.add(new QItem(root, 0)); // Horizontal distance of root is 0
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// Standard BFS or level order traversal loop
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while (!Q.isEmpty()) {
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// Remove the front item and get its details
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QItem qi = Q.remove();
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int hd = qi.hd;
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TreeNode n = qi.node;
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// If this is the first node at its horizontal distance,
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// then this node is in top view
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if (!set.contains(hd)) {
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set.add(hd);
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System.out.print(n.key + " ");
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}
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// Enqueue left and right children of current node
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if (n.left != null) Q.add(new QItem(n.left, hd - 1));
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if (n.right != null) Q.add(new QItem(n.right, hd + 1));
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}
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}
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}
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// Driver class to test above methods
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public class PrintTopViewofTree {
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public static void main(String[] args) {
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/* Create following Binary Tree
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1
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/ \
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2 3
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\
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4
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\
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5
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\
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6*/
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TreeNode root = new TreeNode(1);
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root.left = new TreeNode(2);
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root.right = new TreeNode(3);
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root.left.right = new TreeNode(4);
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root.left.right.right = new TreeNode(5);
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root.left.right.right.right = new TreeNode(6);
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Tree t = new Tree(root);
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System.out.println("Following are nodes in top view of Binary Tree");
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t.printTopView();
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}
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}
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