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BinaryTreeLevelOrderTraversal.java

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import java.util.*;

/**

* Created by YGZ on 2016/5/13.

* My email : gzyang1125@foxmail.com

*/

public class BinaryTreeLevelOrderTraversal {

public List<List<Integer>> levelOrder(TreeNode root) {

List<List<Integer>> res = new LinkedList<List<Integer>>();

if (root==null) return res;

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

Queue<TreeNode> queue1 = new LinkedList<TreeNode>();

queue.add(root);

while (!queue.isEmpty()||!queue1.isEmpty()) {

while (!queue.isEmpty()) {

TreeNode tem = queue.poll();

queue1.add(tem);

}

List<Integer> list = new ArrayList<Integer>();

while (!queue1.isEmpty()) {

TreeNode treeNode = queue1.poll();

list.add(treeNode.val);

if (treeNode.left!=null){queue.add(treeNode.left);}

if (treeNode.right!=null){queue.add(treeNode.right);}

}

res.add(list);

}

return res;

}

public static void main(String[] args){

TreeNode treeNode = new TreeNode(1);

BinaryTreeLevelOrderTraversal binaryTreeLevelOrderTraversal = new BinaryTreeLevelOrderTraversal();

System.out.println(binaryTreeLevelOrderTraversal.levelOrder(treeNode));

}

}