二叉树层序遍历，使用队列

参考：程序员小灰

 

package chapter3.part2; import java.util.Arrays; import java.util.LinkedList; import java.util.Queue; import org.junit.Test; public class BinaryTreeFindWithQueue { @Test public void levelPrintBinaryTree() { LinkedList<Integer> inputList = new LinkedList<Integer>(Arrays. asList(new Integer[] {3,2,9,null,null,10,null,null,8,null,4})); TreeNode root = createBinary(inputList); System.out.println("二叉树层序遍历："); printBinaryTreeWithQueue(root); } private void printBinaryTreeWithQueue(TreeNode root) { Queue<TreeNode> queue = new LinkedList<TreeNode>();//通过LinkedList创建队列 queue.offer(root); while(!queue.isEmpty()) { TreeNode node = queue.poll(); System.out.println(node.data); //甩掉本元素时，让自己的左右孩子入队列，追加到队尾 if(node.leftNode != null) { queue.offer(node.leftNode); } if(node.rightNode != null) { queue.offer(node.rightNode); } } } private TreeNode createBinary(LinkedList<Integer> inputList) { TreeNode node = null; if(inputList == null || inputList.isEmpty()) { return null; } Integer data = inputList.removeFirst(); if(data != null) { node = new TreeNode(data); node.leftNode = createBinary(inputList); node.rightNode = createBinary(inputList); } return node; } }

 

注意：       要通过LinkedList创建队列

 Queue<TreeNode> queue = new LinkedList<TreeNode>();

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