题解 | #求二叉树的层序遍历#
求二叉树的层序遍历
https://www.nowcoder.com/practice/04a5560e43e24e9db4595865dc9c63a3
import java.util.*;
/*
* public class TreeNode {
* int val = 0;
* TreeNode left = null;
* TreeNode right = null;
* public TreeNode(int val) {
* this.val = val;
* }
* }
*/
public class Solution {
/**
* 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
*
*
* @param root TreeNode类
* @return int整型ArrayList<ArrayList<>>
*/
public ArrayList<ArrayList<Integer>> levelOrder (TreeNode root) {
// write code here
ArrayList<ArrayList<Integer>> list = new ArrayList<>();
level(list,0,root);
return list;
}
private void level(ArrayList<ArrayList<Integer>> list, int i, TreeNode root) {
// TODO
if(root==null){
return;
}
if(list.size()<=i){
list.add(new ArrayList<Integer>());
}
list.get(i).add(root.val);
level(list,i+1,root.left);
level(list,i+1,root.right);
}
}
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