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Merge pull request #1872 from LookSin/new-commit

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257.给Java解法添加更全面清晰的注释，另修改一处重复的笔误
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程序员Carl
2023-01-28 10:18:11 +08:00
committed by GitHub
parent 7850267182 026f8ca7b4
commit 50c5d846d6
1 changed files with 14 additions and 12 deletions
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26
problems/0257.二叉树的所有路径.md
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@ -34,7 +34,7 @@
## 递归 ## 递归
1. 递归函数函数参数以及返回值 1. 递归函数参数以及返回值
要传入根节点，记录每一条路径的path，和存放结果集的result，这里递归不需要返回值，代码如下： 要传入根节点，记录每一条路径的path，和存放结果集的result，这里递归不需要返回值，代码如下：
@ -259,7 +259,7 @@ if (cur->right) {
path.pop_back(); // 回溯 '>' path.pop_back(); // 回溯 '>'
path.pop_back(); // 回溯 '-' path.pop_back(); // 回溯 '-'
} }
``` ```
整体代码如下： 整体代码如下：
@ -395,33 +395,34 @@ class Solution {
* 递归法 * 递归法
*/ */
public List<String> binaryTreePaths(TreeNode root) { public List<String> binaryTreePaths(TreeNode root) {
List<String> res = new ArrayList<>(); List<String> res = new ArrayList<>();// 存最终的结果
if (root == null) { if (root == null) {
return res; return res;
} }
List<Integer> paths = new ArrayList<>(); List<Integer> paths = new ArrayList<>();// 作为结果中的路径
traversal(root, paths, res); traversal(root, paths, res);
return res; return res;
} }
private void traversal(TreeNode root, List<Integer> paths, List<String> res) { private void traversal(TreeNode root, List<Integer> paths, List<String> res) {
paths.add(root.val); paths.add(root.val);// 前序遍历，中
// 叶子结点 // 遇到叶子结点
if (root.left == null && root.right == null) { if (root.left == null && root.right == null) {
// 输出 // 输出
StringBuilder sb = new StringBuilder(); StringBuilder sb = new StringBuilder();// StringBuilder用来拼接字符串，速度更快
for (int i = 0; i < paths.size() - 1; i++) { for (int i = 0; i < paths.size() - 1; i++) {
sb.append(paths.get(i)).append("->"); sb.append(paths.get(i)).append("->");
} }
sb.append(paths.get(paths.size() - 1)); sb.append(paths.get(paths.size() - 1));// 记录最后一个节点
res.add(sb.toString()); res.add(sb.toString());// 收集一个路径
return; return;
} }
if (root.left != null) { // 递归和回溯是同时进行，所以要放在同一个花括号里
if (root.left != null) { // 左
traversal(root.left, paths, res); traversal(root.left, paths, res);
paths.remove(paths.size() - 1);// 回溯 paths.remove(paths.size() - 1);// 回溯
} }
if (root.right != null) { if (root.right != null) { // 右
traversal(root.right, paths, res); traversal(root.right, paths, res);
paths.remove(paths.size() - 1);// 回溯 paths.remove(paths.size() - 1);// 回溯
} }
@ -794,7 +795,7 @@ object Solution {
} }
} }
``` ```
rust: rust:
```rust ```rust
@ -826,3 +827,4 @@ impl Solution {
<a href="https://programmercarl.com/other/kstar.html" target="_blank"> <a href="https://programmercarl.com/other/kstar.html" target="_blank">
<img src="../pics/网站星球宣传海报.jpg" width="1000"/> <img src="../pics/网站星球宣传海报.jpg" width="1000"/>
</a> </a>