每日一练_118(2021.10.30) 对称二叉树。

原创于 2021-10-30 21:16:36 发布 · 137 阅读

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菜鸟的每天一练。同时被 2 个专栏收录

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分享作为班长的经历，探讨如何用编程思维解决班级事务管理问题，如对称树算法在平衡任务分配中的应用。

最近莫名其妙的当上了班长，开学后事情还挺多。平常晚上练了点题，也懒得记录到这里了。

作者：LeetCode-Solution
链接：https://leetcode-cn.com/problems/symmetric-tree/solution/dui-cheng-er-cha-shu-by-leetcode-solution/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

个人微改：

import java.util.LinkedList;
import java.util.Queue;

/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Symmetric{
   public boolean isSymmetric(TreeNode root) {
       return check(root,root);
   }

   public boolean check(TreeNode p,TreeNode q) {
       if(p == null && q == null) {
           return true;
       }
       if(p == null || q == null) {
           return false;
       }
       return p.val == q.val && check(p.left, q.right) && check(p.right, q.left);
   }
}
public class SymmetricTree {

   public static void main(String[] args) {
       // TODO Auto-generated method stub
       String str1 = "[1,2,3]";
       String str2 = "[1,2,2]";
       TreeNode root1 = stringToTreeNode(str1);
       TreeNode root2 = stringToTreeNode(str2);
       boolean flag = new Symmetric().isSymmetric(root1);
       System.out.println(flag);
       boolean flag2 = new Symmetric().isSymmetric(root2);
       System.out.println(flag2);
   }

   public static TreeNode stringToTreeNode(String input) {
       input = input.trim();
       input = input.substring(1,input.length()-1);
       if(input.length()==0) {
           return null;
       }

       String[] parts = input.split(",");
       String item = parts[0];
       TreeNode root = new TreeNode(Integer.parseInt(item));
       Queue<TreeNode> nodeQueue = new LinkedList<>();
       nodeQueue.add(root);

       int index = 1;
       while(!nodeQueue.isEmpty()) {
           TreeNode node = nodeQueue.remove();

           if(index == parts.length) {
               break;
           }

           item = parts[index++];
           item = item.trim();
           if(!item.equals("null")) {
               int leftNumber = Integer.parseInt(item);
               node.left = new TreeNode(leftNumber);
               nodeQueue.add(node.left);
           }

           if(index == parts.length) {
               break;
           }

           item = parts[index++];
           item = item.trim();
           if(!item.equals("null")) {
               int rightNumber = Integer.parseInt(item);
               node.right = new TreeNode(rightNumber);
               nodeQueue.add(node.right);
           }
       }
       return root;
   }

   public static String booleanToString(boolean input) {
       return input?"True":"False";
   }