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‎.dev/logs.json‎

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"sols": {
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"stack_using_queues.go": "2763c912408f75bca695972611c5e714babc32f989bda656393cd4af447a6aaa"
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}
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"sols": {
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"invert_binary_tree.go": "593e11b04a9d4e0995eee40c612eeb3b344fad616b38f33523fc60a981dd1a64"
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"sols": {
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‎README.md‎

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[**_Rejection Sampling_**][rejection sampling]  • 
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[**_Biconnected Component_**][biconnected component]
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### **Total Problems Solved: _105_**
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### **Total Problems Solved: _108_**
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---
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‎TOPICWISE.md‎

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| **0145** | [Binary Tree Postorder Traversal][145] | Stack, Tree, DFS, Binary Tree | ![][easy] | |
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| **0199** | [Binary Tree Right Side View][199] | Tree, DFS, BFS, Binary Tree | ![][medium] | |
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| **0222** | [Count Complete Tree Nodes][222] | Binary Search, Tree, DFS, Binary Tree | ![][medium] | |
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| **0226** | [Invert Binary Tree][226] | Tree, Depth-First Search, Breadth-First Search, Binary Tree | ![][easy] | |
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| **0230** | [Kth Smallest Element in a BST ][230] | Tree, DFS, BST, Binary Tree | ![][medium] | |
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| **0236** | [Lowest Common Ancestor of a Binary Tree][236] | Tree, Depth-First Search, Binary Tree | ![][medium] | |
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| **0337** | [House Robber III][337] | DP, Tree, DFS, Binary Tree | ![][medium] | |
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| **0145** | [Binary Tree Postorder Traversal][145] | Stack, Tree, DFS, Binary Tree | ![][easy] | |
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| **0199** | [Binary Tree Right Side View][199] | Tree, DFS, BFS, Binary Tree | ![][medium] | |
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| **0222** | [Count Complete Tree Nodes][222] | Binary Search, Tree, DFS, Binary Tree | ![][medium] | |
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| **0226** | [Invert Binary Tree][226] | Tree, Depth-First Search, Breadth-First Search, Binary Tree | ![][easy] | |
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| **0230** | [Kth Smallest Element in a BST ][230] | Tree, DFS, BST, Binary Tree | ![][medium] | |
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| **0236** | [Lowest Common Ancestor of a Binary Tree][236] | Tree, Depth-First Search, Binary Tree | ![][medium] | |
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| **0337** | [House Robber III][337] | DP, Tree, DFS, Binary Tree | ![][medium] | |
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| **0094** | [Binary Tree Inorder Traversal][94] | Tree, Stack, DFS, Binary Tree | ![][easy] | |
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| **0144** | [Binary Tree Preorder Traversal][144] | Stack, Tree, DFS, Binary Tree | ![][easy] | |
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| **0145** | [Binary Tree Postorder Traversal][145] | Stack, Tree, DFS, Binary Tree | ![][easy] | |
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| **0225** | [Implement Stack using Queues][225] | ST, Design, Q | ![][easy] | |
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| **0232** | [Implement Queue using Stacks][232] | ST, Design, Q | ![][easy] | |
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| **0445** | [Add Two Numbers II][445] | Linked List, Math, Stack | ![][medium] | |
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| **0739** | [Daily Temperatures][739] | Array, Stack, Monotonic Stack | ![][medium] | |
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| **1047** | [Remove All Adjacent Duplicates In String][1047] | String, Stack | ![][easy] | |
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## Design
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| # | Solution | Tags | Difficulty | Remark |
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| :-: | :------: | :--: | :--------: | :----: |
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| # | Solution | Tags | Difficulty | Remark |
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| :------: | :---------------------------------: | :-----------: | :--------: | :----: |
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| **0225** | [Implement Stack using Queues][225] | ST, Design, Q | ![][easy] | |
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| **0232** | [Implement Queue using Stacks][232] | ST, Design, Q | ![][easy] | |
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<!---------------------------------{ Solution Table }-------------------------->
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## Queue
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| # | Solution | Tags | Difficulty | Remark |
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| :-: | :------: | :--: | :--------: | :----: |
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| # | Solution | Tags | Difficulty | Remark |
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| :------: | :---------------------------------: | :-----------: | :--------: | :----: |
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| **0225** | [Implement Stack using Queues][225] | ST, Design, Q | ![][easy] | |
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| **0232** | [Implement Queue using Stacks][232] | ST, Design, Q | ![][easy] | |
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<!---------------------------------{ Solution Table }-------------------------->
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[217]: ./src/0201-0300/217%20-%20Contains%20Duplicate/
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[219]: ./src/0201-0300/219%20-%20Contains%20Duplicate%20II/
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[222]: ./src/0201-0300/222%20-%20Count%20Complete%20Tree%20Nodes/
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[225]: ./src/0201-0300/225%20-%20Implement%20Stack%20using%20Queues/
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[226]: ./src/0201-0300/226%20-%20Invert%20Binary%20Tree/
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[230]: ./src/0201-0300/230%20-%20Kth%20Smallest%20Element%20in%20a%20BST/
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[231]: ./src/0201-0300/231%20-%20Power%20of%20Two/
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[232]: ./src/0201-0300/232%20-%20Implement%20Queue%20using%20Stacks/
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[236]: ./src/0201-0300/236%20-%20Lowest%20Common%20Ancestor%20of%20a%20Binary%20Tree/
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[239]: ./src/0201-0300/239%20-%20Sliding%20Window%20Maximum/
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[278]: ./src/0201-0300/278%20-%20First%20Bad%20Version/

‎docs/index.md‎

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[**_Rejection Sampling_**][rejection sampling] &nbsp;•&nbsp;
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[**_Biconnected Component_**][biconnected component]
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### **Total Problems Solved: _105_**
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### **Total Problems Solved: _108_**
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## Contributors
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‎src/0201-0300/225 - Implement Stack using Queues/README.md‎

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# 225. Implement Stack using Queues [![share]](https://leetcode.com/problems/implement-stack-using-queues/)
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![][easy]
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## Problem Statement
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<p>Implement a last-in-first-out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal stack (<code>push</code>, <code>top</code>, <code>pop</code>, and <code>empty</code>).</p>
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<p>Implement the <code>MyStack</code> class:</p>
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<ul>
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<li><code>void push(int x)</code> Pushes element x to the top of the stack.</li>
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<li><code>int pop()</code> Removes the element on the top of the stack and returns it.</li>
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<li><code>int top()</code> Returns the element on the top of the stack.</li>
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<li><code>boolean empty()</code> Returns <code>true</code> if the stack is empty, <code>false</code> otherwise.</li>
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</ul>
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<p><b>Notes:</b></p>
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<ul>
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<li>You must use <strong>only</strong> standard operations of a queue, which means that only <code>push to back</code>, <code>peek/pop from front</code>, <code>size</code> and <code>is empty</code> operations are valid.</li>
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<li>Depending on your language, the queue may not be supported natively. You may simulate a queue using a list or deque (double-ended queue) as long as you use only a queue's standard operations.</li>
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</ul>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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```
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Input
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["MyStack", "push", "push", "top", "pop", "empty"]
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[[], [1], [2], [], [], []]
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Output
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[null, null, null, 2, 2, false]
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Explanation
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MyStack myStack = new MyStack();
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myStack.push(1);
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myStack.push(2);
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myStack.top(); // return 2
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myStack.pop(); // return 2
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myStack.empty(); // return False
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```
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 &lt;= x &lt;= 9</code></li>
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<li>At most <code>100</code> calls will be made to <code>push</code>, <code>pop</code>, <code>top</code>, and <code>empty</code>.</li>
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<li>All the calls to <code>pop</code> and <code>top</code> are valid.</li>
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</ul>
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<p> </p>
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<p><strong>Follow-up:</strong> Can you implement the stack using only one queue?</p>
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## Solutions
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### [_Go_](stack_using_queues.go)
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```go [Go]
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package main
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type MyStack struct {
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queue []int
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}
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func Constructor() MyStack {
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return MyStack{}
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}
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// Push x onto stack.
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func (this *MyStack) Push(x int) {
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this.queue = append(this.queue, x)
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}
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// Removes and returns the element on top of the stack
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func (this *MyStack) Pop() int {
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if len(this.queue) == 0 {
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return 0
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}
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pop := this.queue[len(this.queue)-1]
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this.queue = this.queue[:len(this.queue)-1]
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return pop
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}
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// Get the top element.
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func (this *MyStack) Top() int {
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if len(this.queue) == 0 {
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return 0
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}
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return this.queue[len(this.queue)-1]
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}
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// Return whether the stack is empty.
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func (this *MyStack) Empty() bool {
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return len(this.queue) == 0
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}
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```
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### [_..._]()
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```
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```
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<!----------------------------------{ link }--------------------------------->
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[share]: https://graph.org/file/3ea5234dda646b71c574a.png
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[easy]: https://img.shields.io/badge/Difficulty-Easy-bright.svg
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[medium]: https://img.shields.io/badge/Difficulty-Medium-yellow.svg
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[hard]: https://img.shields.io/badge/Difficulty-Hard-red.svg

‎src/0201-0300/226 - Invert Binary Tree/README.md‎

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# 226. Invert Binary Tree [![share]](https://leetcode.com/problems/invert-binary-tree/)
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![][easy]
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## Problem Statement
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<p>Given the <code>root</code> of a binary tree, invert the tree, and return <em>its root</em>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/03/14/invert1-tree.jpg" style="width: 500px; height: 165px;"/>
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```
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Input: root = [4,2,7,1,3,6,9]
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Output: [4,7,2,9,6,3,1]
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```
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/03/14/invert2-tree.jpg" style="width: 500px; height: 120px;"/>
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```
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Input: root = [2,1,3]
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Output: [2,3,1]
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```
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<p><strong class="example">Example 3:</strong></p>
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```
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Input: root = []
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Output: []
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```
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li>The number of nodes in the tree is in the range <code>[0, 100]</code>.</li>
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<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
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</ul>
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## Solutions
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### [_Go_](invert_binary_tree.go)
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```go [Go]
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package main
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// Definition for a binary tree node.
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type TreeNode struct {
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Val int
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Left *TreeNode
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Right *TreeNode
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}
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func invertTree(root *TreeNode) *TreeNode {
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if root == nil {
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return nil
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}
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invertTree(root.Left)
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invertTree(root.Right)
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root.Left, root.Right = root.Right, root.Left
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return root
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}
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```
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### [_..._]()
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```
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```
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<!----------------------------------{ link }--------------------------------->
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[share]: https://graph.org/file/3ea5234dda646b71c574a.png
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[easy]: https://img.shields.io/badge/Difficulty-Easy-bright.svg
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[medium]: https://img.shields.io/badge/Difficulty-Medium-yellow.svg
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[hard]: https://img.shields.io/badge/Difficulty-Hard-red.svg

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