78 lines
2.8 KiB
Java
78 lines
2.8 KiB
Java
package com.dsa.trees;
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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.io.IOException;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Queue;
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public class LevelOrderTraversal {
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public static void main(String[] args) {
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try (BufferedReader reader = new BufferedReader(new FileReader("input.txt"))) {
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String[] elements = reader.readLine().trim().split(",");
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Queue<TreeNode> queue = new LinkedList<>();
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TreeNode root = new TreeNode(Integer.parseInt(elements[0]));
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queue.offer(root);
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int index = 1;
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while (!queue.isEmpty() && index < elements.length) {
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TreeNode node = queue.poll();
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if (!elements[index].equalsIgnoreCase("null")) {
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node.left = new TreeNode(Integer.parseInt(elements[index]));
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queue.offer(node.left);
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}
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index++;
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if (!elements[index].equalsIgnoreCase("null")) {
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node.right = new TreeNode(Integer.parseInt(elements[index]));
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queue.offer(node.right);
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}
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index++;
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}
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List<List<Integer>> list = levelOrderBottom(root);
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for (List<Integer> level : list) {
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System.out.println(level);
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}
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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}
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public static List<List<Integer>> levelOrder(TreeNode root) {
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List<List<Integer>> res = new LinkedList<>();
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if (root == null) return res;
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Queue<TreeNode> queue = new LinkedList<>();
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queue.offer(root);
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while (!queue.isEmpty()) {
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List<Integer> list = new LinkedList<>();
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int size = queue.size();
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for (int i = 0; i < size; i++) {
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TreeNode node = queue.poll();
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list.add(node.val);
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if (node.left != null) queue.offer(node.left);
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if (node.right != null) queue.offer(node.right);
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}
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res.add(list);
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}
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return res;
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}
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public static List<List<Integer>> levelOrderBottom(TreeNode root) {
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List<List<Integer>> res = new LinkedList<>();
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if (root == null) return res;
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Queue<TreeNode> queue = new LinkedList<>();
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queue.offer(root);
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while (!queue.isEmpty()) {
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List<Integer> list = new LinkedList<>();
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int size = queue.size();
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for (int i = 0; i < size; i++) {
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TreeNode node = queue.poll();
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list.add(node.val);
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if (node.left != null) queue.offer(node.left);
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if (node.right != null) queue.offer(node.right);
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}
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res.addFirst(list);
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}
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return res;
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}
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}
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