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67 lines
1.7 KiB
Java
67 lines
1.7 KiB
Java
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# LeetCode 第 94 号问题：二叉树的中序遍历
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> 本文首发于公众号「图解面试算法」，是 [图解 LeetCode ](<https://github.com/MisterBooo/LeetCodeAnimation>) 系列文章之一。
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>
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> 同步博客：https://www.algomooc.com
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题目来源于 LeetCode 上第 94 号问题：二叉树的中序遍历。题目难度为 Medium，目前通过率为 35.8% 。
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### 题目描述
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给定一个二叉树，返回它的*中序* 遍历。
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**示例:**
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```
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输入: [1,null,2,3]
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1
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\
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2
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/
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3
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输出: [1,3,2]
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```
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**进阶:** 递归算法很简单，你可以通过迭代算法完成吗？
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### 题目解析
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用**栈(Stack)**的思路来处理问题。
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中序遍历的顺序为**左-根-右**，具体算法为：
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- 从根节点开始，先将根节点压入栈
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- 然后再将其所有左子结点压入栈，取出栈顶节点，保存节点值
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- 再将当前指针移到其右子节点上，若存在右子节点，则在下次循环时又可将其所有左子结点压入栈中
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### 动画描述
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### 代码实现
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```
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class Solution {
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public List<Integer> inorderTraversal(TreeNode root) {
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List<Integer> list = new ArrayList<>();
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Stack<TreeNode> stack = new Stack<>();
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TreeNode cur = root;
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while (cur != null || !stack.isEmpty()) {
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if (cur != null) {
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stack.push(cur);
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cur = cur.left;
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} else {
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cur = stack.pop();
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list.add(cur.val);
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cur = cur.right;
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}
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}
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return list;
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}
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}
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```
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