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package byteDance;

import java.util.ArrayList;

import java.util.LinkedList;

import java.util.List;

import java.util.Queue;

/**

* Created by lizeyang on 2020/5/15.

* 二叉树的各层节点数

*/

public class test32 {

//非递归实现

public static List<Integer> test(TreeNode root) {

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

if (root == null) {

return list;

}

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

queue.offer(root);

while (!queue.isEmpty()) {

int size = queue.size();

list.add(size);

for (int i = 0; i < size; i++) {

TreeNode node = queue.poll();

if (node.left != null) {

queue.offer(node.left);

}

if (node.right != null) {

queue.offer(node.right);

}

}

}

return list;

}

//递归实现

static List<List<Integer>> res = new ArrayList<>();

public static List<Integer> levelTraverse(TreeNode root){

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

if(root==null){

return new ArrayList<>();

}

int depth = getDepth(root);

for(int i=0;i<depth;i++){

res.add(new ArrayList<>());

}

printNodeAtLevel(root,res,0);

for(int i=0;i<res.size();i++) {

list.add(res.get(i).size());

}

return list;

}

public static void printNodeAtLevel(TreeNode root,List<List<Integer>> res,int level){

if(root==null){

return;

}

res.get(level).add(root.val);

printNodeAtLevel(root.left,res,level+1);

printNodeAtLevel(root.right,res,level+1);

}

public static int getDepth(TreeNode root){

if(root==null){

return 0;

}

if(root.left==null){

return getDepth(root.right)+1;

}

if(root.right==null){

return getDepth(root.left)+1;

}

return Math.max(getDepth(root.left),getDepth(root.right))+1;

}

public static void main(String[] args) {

TreeNode root = new TreeNode(5);

root.left = new TreeNode(4);

root.right = new TreeNode(8);

root.left.left = new TreeNode(3);

root.right.left = new TreeNode(7);

root.right.left.left = new TreeNode(6);

root.right.right = new TreeNode(9);

//非递归调用

// List<Integer> res = test(root);

//递归调用

List<Integer> res = levelTraverse(root);

for (int i = 0; i < res.size(); i++) {

System.out.print(res.get(i) + " ");

}

}

}