From b8f430ad10bc9b316d22144fdf1d876b2f9a9819 Mon Sep 17 00:00:00 2001 From: zhangsan <646228430@qq.com> Date: Sat, 5 Jul 2025 18:04:10 +0800 Subject: [PATCH] =?UTF-8?q?7.5=20=E5=9B=BE=E8=AE=BA+=E5=9B=9E=E6=BA=AF?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- src/main/java/backtrack/Permute.java | 31 +++++++++++++-- src/main/java/backtrack/Subsets.java | 2 + src/main/java/backtrack/SubsetsWithDup.java | 3 +- src/main/java/graph/CanFinish.java | 2 + src/main/java/graph/FindOrder.java | 39 +++++++++++++++++-- src/main/java/{graph => 实现类功能}/Trie.java | 3 +- src/test/java/backtrack/SubsetsTest.java | 14 +++++++ .../java/backtrack/SubsetsWithDupTest.java | 2 +- 8 files changed, 86 insertions(+), 10 deletions(-) rename src/main/java/{graph => 实现类功能}/Trie.java (98%) create mode 100644 src/test/java/backtrack/SubsetsTest.java diff --git a/src/main/java/backtrack/Permute.java b/src/main/java/backtrack/Permute.java index 7b56565..562bfdb 100644 --- a/src/main/java/backtrack/Permute.java +++ b/src/main/java/backtrack/Permute.java @@ -9,19 +9,44 @@ import java.util.List; *示例 1： * 输入：nums = [1,2,3] * 输出：[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] - * + * 示例 2： * 输入：nums = [0,1] * 输出：[[0,1],[1,0]] - * + * 示例 3： * 输入：nums = [1] * 输出：[[1]] - * + * 链接：https://leetcode.cn/problems/permutations/ */ +//二刷会做 public class Permute { + void dfs(List>res,Listpath,int[] nums,boolean[] used){ + if(path.size()==nums.length) { + res.add(new ArrayList<>(path)); + return; + } + for (int i = 0; i < nums.length; i++) { + if(used[i])continue; + used[i]=true; + path.add(nums[i]); + dfs(res,path,nums,used); + path.remove(path.size()-1); + used[i]=false; + } + } + public List> permute2(int[] nums) { + List>res=new ArrayList<>(); + Listpath=new ArrayList<>(); + boolean[] used=new boolean[nums.length]; + dfs(res,path,nums,used); + return res; + } + + + public List> permute(int[] nums) { List> res = new ArrayList<>(); // 用来标记数组中数字是否被使用 diff --git a/src/main/java/backtrack/Subsets.java b/src/main/java/backtrack/Subsets.java index dedb279..cc9ec5a 100644 --- a/src/main/java/backtrack/Subsets.java +++ b/src/main/java/backtrack/Subsets.java @@ -18,7 +18,9 @@ import java.util.List; * 链接：https://leetcode.cn/problems/subsets/ */ +//二刷会做 public class Subsets { + public List> subsets(int[] nums) { List> res = new ArrayList<>(); List path = new ArrayList<>(); diff --git a/src/main/java/backtrack/SubsetsWithDup.java b/src/main/java/backtrack/SubsetsWithDup.java index 88bc0c2..b685b58 100644 --- a/src/main/java/backtrack/SubsetsWithDup.java +++ b/src/main/java/backtrack/SubsetsWithDup.java @@ -17,6 +17,7 @@ import java.util.List; */ //不会，有点难 public class SubsetsWithDup { + public List> subsetsWithDup(int[] nums) { List> res = new ArrayList<>(); List path = new ArrayList<>(); @@ -43,7 +44,7 @@ public class SubsetsWithDup { // 测试方法 public static void main(String[] args) { SubsetsWithDup solution = new SubsetsWithDup(); - int[] nums = {1, 2, 2}; + int[] nums = {1, 2, 3}; List> subsets = solution.subsetsWithDup(nums); System.out.println(subsets); // 输出：[[], [1], [1, 2], [1, 2, 2], [2], [2, 2]] diff --git a/src/main/java/graph/CanFinish.java b/src/main/java/graph/CanFinish.java index c45b2ef..1fbe677 100644 --- a/src/main/java/graph/CanFinish.java +++ b/src/main/java/graph/CanFinish.java @@ -15,6 +15,7 @@ import java.util.Queue; * 链接：https://leetcode.cn/problems/course-schedule/ */ + //思路知道，代码不好写 /* 思路解析 @@ -32,6 +33,7 @@ import java.util.Queue; 判断是否存在环 如果最终能处理的课程数量等于总课程数，则说明不存在环路，所有课程都可以按要求完成；否则说明存在循环依赖，无法完成所有课程。 */ +//二刷不会 public class CanFinish { public boolean canFinish(int numCourses, int[][] prerequisites) { // 构建图：graph.get(i) 存储课程 i 的后续课程 diff --git a/src/main/java/graph/FindOrder.java b/src/main/java/graph/FindOrder.java index 7a06ccb..6452374 100644 --- a/src/main/java/graph/FindOrder.java +++ b/src/main/java/graph/FindOrder.java @@ -1,9 +1,6 @@ package graph; -import java.util.ArrayDeque; -import java.util.ArrayList; -import java.util.List; -import java.util.Queue; +import java.util.*; /** * 题目： 210. 课程表 II (findOrder) @@ -19,7 +16,41 @@ import java.util.Queue; * 链接：https://leetcode.cn/problems/course-schedule-ii/ */ +//二刷会做（先把207做了就会） public class FindOrder { + public int[] findOrder2(int numCourses, int[][] prerequisites) { + int[] indgree=new int[numCourses]; + List>graph=new ArrayList<>(); + int[] res=new int[numCourses]; + Queuequeue=new LinkedList<>(); + for (int i = 0; i < numCourses; i++) { + graph.add(new ArrayList<>()); + } + for (int i = 0; i < prerequisites.length; i++) { + int course=prerequisites[i][0]; + int precourse=prerequisites[i][1]; + indgree[course]++; + graph.get(precourse).add(course); + } + for (int i = 0; i < numCourses; i++) { + if(indgree[i]==0) + queue.add(i); + } + int count=0; + while (!queue.isEmpty()){ + int precourse=queue.poll(); + res[count]=precourse; + count++; + for (Integer course : graph.get(precourse)) { + indgree[course]--; + if(indgree[course]==0) + queue.add(course); + } + } + if(count==numCourses) return res; + else return new int[0]; + } + public int[] findOrder(int numCourses, int[][] prerequisites) { int[] indegree=new int[numCourses]; int[] res=new int[numCourses]; diff --git a/src/main/java/graph/Trie.java b/src/main/java/实现类功能/Trie.java similarity index 98% rename from src/main/java/graph/Trie.java rename to src/main/java/实现类功能/Trie.java index a3c7e35..26ac9ef 100644 --- a/src/main/java/graph/Trie.java +++ b/src/main/java/实现类功能/Trie.java @@ -1,4 +1,4 @@ -package graph; +package 实现类功能; /** * 题目： 208. 实现 Trie (前缀树) * 描述：Trie（发音类似 "try"）或者说 前缀树 是一种树形数据结构，用于高效地存储和检索字符串数据集中的键。这一数据结构有相当多的应用情景，例如自动补全和拼写检查。 @@ -33,6 +33,7 @@ package graph; * 共用方法 (searchPrefix) * 将插入和查找里的公共逻辑抽取出来：遍历路径、空指针检查、节点推进。 */ +//二刷不会 学习 //https://leetcode.cn/problems/implement-trie-prefix-tree/solutions/98390/trie-tree-de-shi-xian-gua-he-chu-xue-zhe-by-huwt/?envType=study-plan-v2&envId=top-interview-150 class Trie { // children 数组保存当前节点的所有子节点，索引 0-25 分别对应 'a'-'z' diff --git a/src/test/java/backtrack/SubsetsTest.java b/src/test/java/backtrack/SubsetsTest.java new file mode 100644 index 0000000..ef7b5f5 --- /dev/null +++ b/src/test/java/backtrack/SubsetsTest.java @@ -0,0 +1,14 @@ +package backtrack; + +import junit.framework.TestCase; + +import java.util.List; + +public class SubsetsTest extends TestCase { + + public void testSubsets() { + int[]nums = {1,2,3}; + Subsets solution = new Subsets(); + List> subsets = solution.subsets(nums); + } +} \ No newline at end of file diff --git a/src/test/java/backtrack/SubsetsWithDupTest.java b/src/test/java/backtrack/SubsetsWithDupTest.java index be385af..86b8b90 100644 --- a/src/test/java/backtrack/SubsetsWithDupTest.java +++ b/src/test/java/backtrack/SubsetsWithDupTest.java @@ -10,7 +10,7 @@ public class SubsetsWithDupTest { @Test public void subsetsWithDup() { - int[]nums = {1,2,2}; + int[]nums = {1,2,3}; SubsetsWithDup solution = new SubsetsWithDup(); List>res=solution.subsetsWithDup(nums); System.out.println(res);