algorithm/leetcode-master
1
0
Fork 0
mirror of https://github.com/youngyangyang04/leetcode-master.git synced 2025-07-09 03:34:02 +08:00
Code Issues Packages Projects Releases Wiki Activity

Update 0101.对称二叉树.md

Browse Source 
添加 0101.对称二叉树 Java版本，3种解法
This commit is contained in:
Joshua
2021-05-14 01:35:48 +08:00
committed by GitHub
parent 1f5408b160
commit 9cf58adff3
1 changed files with 99 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

100
problems/0101.对称二叉树.md
View File

@ -254,7 +254,105 @@ public:
## 其他语言版本
Java：
```Java
/**
* 递归法
*/
public boolean isSymmetric1(TreeNode root) {
return compare(root.left, root.right);
}
private boolean compare(TreeNode left, TreeNode right) {
if (left == null && right != null) {
return false;
}
if (left != null && right == null) {
return false;
}
if (left == null && right == null) {
return true;
}
if (left.val != right.val) {
return false;
}
// 比较外侧
boolean compareOutside = compare(left.left, right.right);
// 比较内侧
boolean compareInside = compare(left.right, right.left);
return compareOutside && compareInside;
}
/**
* 迭代法
* 使用双端队列，相当于两个栈
*/
public boolean isSymmetric2(TreeNode root) {
Deque<TreeNode> deque = new LinkedList<>();
deque.offerFirst(root.left);
deque.offerLast(root.right);
while (!deque.isEmpty()) {
TreeNode leftNode = deque.pollFirst();
TreeNode rightNode = deque.pollLast();
if (leftNode == null && rightNode == null) {
continue;
}
// if (leftNode == null && rightNode != null) {
// return false;
// }
// if (leftNode != null && rightNode == null) {
// return false;
// }
// if (leftNode.val != rightNode.val) {
// return false;
// }
// 以上三个判断条件合并
if (leftNode == null || rightNode == null || leftNode.val != rightNode.val) {
return false;
}
deque.offerFirst(leftNode.left);
deque.offerFirst(leftNode.right);
deque.offerLast(rightNode.right);
deque.offerLast(rightNode.left);
}
return true;
}
/**
* 迭代法
* 使用普通队列
*/
public boolean isSymmetric3(TreeNode root) {
Queue<TreeNode> deque = new LinkedList<>();
deque.offer(root.left);
deque.offer(root.right);
while (!deque.isEmpty()) {
TreeNode leftNode = deque.poll();
TreeNode rightNode = deque.poll();
if (leftNode == null && rightNode == null) {
continue;
}
// if (leftNode == null && rightNode != null) {
// return false;
// }
// if (leftNode != null && rightNode == null) {
// return false;
// }
// if (leftNode.val != rightNode.val) {
// return false;
// }
// 以上三个判断条件合并
if (leftNode == null || rightNode == null || leftNode.val != rightNode.val) {
return false;
}
// 这里顺序与使用Deque不同
deque.offer(leftNode.left);
deque.offer(rightNode.right);
deque.offer(leftNode.right);
deque.offer(rightNode.left);
}
return true;
}
```
Python：
@ -283,4 +381,4 @@ const check = (leftPtr, rightPtr) => {
* 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
* B站视频：[代码随想录](https://space.bilibili.com/525438321)
* 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>