update: 添加问题“2131.连接两字母单词得到的最长回文串”的代码和题解(#955)

LetMeFly666 · LetMeFly666 · commit 19db0e7e7655 · 2025-05-26T00:10:24.000+08:00
Signed-off-by: LetMeFly666 &lt;814114971@qq.com&gt;
diff --git a/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.cpp b/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.cpp
@@ -0,0 +1,28 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 23:39:17
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-26 00:04:19
+ */
+#if defined(_WIN32) || defined(__APPLE__)
+#include "_[1,2]toVector.h"
+#endif
+
+class Solution {
+public:
+    int longestPalindrome(vector<string>& words) {
+        int cnt[26][26] = {0};
+        for (string& word : words) {
+            cnt[word[0] - 'a'][word[1] - 'a']++;
+        }
+        int ans = 0, middle = 0;
+        for (int i = 0; i < 26; i++) {
+            ans += cnt[i][i] / 2 * 2;
+            middle |= cnt[i][i] % 2;
+            for (int j = i + 1; j < 26; j++) {
+                ans += min(cnt[i][j], cnt[j][i]) * 2;
+            }
+        }
+        return (ans + middle) * 2;
+    }
+};
diff --git a/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.go b/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.go
@@ -0,0 +1,26 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 23:39:17
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-25 23:54:22
+ */
+package main
+
+func longestPalindrome(words []string) int {
+    times := make([][]int, 26)
+    for i := range times {
+        times[i] = make([]int, 26)
+    }
+    for _, word := range words {
+        times[word[0] - 'a'][word[1] - 'a']++
+    }
+    side, mid := 0, 0
+    for i := range times {
+        side += times[i][i] / 2 * 2
+        mid |= times[i][i] % 2
+        for j := i + 1; j < 26; j++ {
+            side += min(times[i][j], times[j][i]) * 2
+        }
+    }
+    return (side + mid) * 2
+}
diff --git a/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.java b/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.java
@@ -0,0 +1,23 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 23:39:17
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-25 23:51:33
+ */
+class Solution {
+    public int longestPalindrome(String[] words) {
+        int[][] times = new int[26][26];
+        for (String word : words) {
+            times[word.charAt(0) - 'a'][word.charAt(1) - 'a']++;
+        }
+        int side = 0, middle = 0;
+        for (int i = 0; i < 26; i++) {
+            side += times[i][i] / 2 * 2;
+            middle |= times[i][i] % 2;
+            for (int j = i + 1; j < 26; j++) {
+                side += Math.min(times[i][j], times[j][i]) * 2;
+            }
+        }
+        return (side + middle) * 2;
+    }
+}
diff --git a/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.py b/Codes/2131-longest-palindrome-by-concatenating-two-letter-words.py
@@ -0,0 +1,20 @@
+'''
+Author: LetMeFly
+Date: 2025-05-25 23:39:17
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-05-25 23:47:11
+'''
+from typing import List
+
+class Solution:
+    def longestPalindrome(self, words: List[str]) -> int:
+        cnt = [[0] * 26 for _ in range(26)]
+        for word in words:
+            cnt[ord(word[0]) - ord('a')][ord(word[1]) - ord('a')] += 1
+        ans = middle = 0
+        for i in range(26):
+            ans += cnt[i][i] // 2 * 2
+            middle |= cnt[i][i] % 2
+            for j in range(i + 1, 26):
+                ans += min(cnt[i][j], cnt[j][i]) * 2
+        return (ans + middle) * 2
diff --git a/README.md b/README.md
@@ -676,6 +676,7 @@
 |2109.向字符串添加空格|中等|<a href="https://leetcode.cn/problems/adding-spaces-to-a-string/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/03/31/LeetCode%202109.%E5%90%91%E5%AD%97%E7%AC%A6%E4%B8%B2%E6%B7%BB%E5%8A%A0%E7%A9%BA%E6%A0%BC/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/146863199" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/adding-spaces-to-a-string/solutions/3635218/letmefly-2109xiang-zi-fu-chuan-tian-jia-cectp/" target="_blank">LeetCode题解</a>|
 |2116.判断一个括号字符串是否有效|中等|<a href="https://leetcode.cn/problems/check-if-a-parentheses-string-can-be-valid/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/03/23/LeetCode%202116.%E5%88%A4%E6%96%AD%E4%B8%80%E4%B8%AA%E6%8B%AC%E5%8F%B7%E5%AD%97%E7%AC%A6%E4%B8%B2%E6%98%AF%E5%90%A6%E6%9C%89%E6%95%88/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/146454056" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/check-if-a-parentheses-string-can-be-valid/solutions/3624225/letmefly-2116pan-duan-yi-ge-gua-hao-zi-f-9n2z/" target="_blank">LeetCode题解</a>|
 |2129.将标题首字母大写|简单|<a href="https://leetcode.cn/problems/capitalize-the-title/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2024/03/11/LeetCode%202129.%E5%B0%86%E6%A0%87%E9%A2%98%E9%A6%96%E5%AD%97%E6%AF%8D%E5%A4%A7%E5%86%99/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/136614914" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/capitalize-the-title/solutions/2679708/letmefly-2129jiang-biao-ti-shou-zi-mu-da-nj90/" target="_blank">LeetCode题解</a>|
+|2131.连接两字母单词得到的最长回文串|中等|<a href="https://leetcode.cn/problems/longest-palindrome-by-concatenating-two-letter-words/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/05/25/LeetCode%202131.%E8%BF%9E%E6%8E%A5%E4%B8%A4%E5%AD%97%E6%AF%8D%E5%8D%95%E8%AF%8D%E5%BE%97%E5%88%B0%E7%9A%84%E6%9C%80%E9%95%BF%E5%9B%9E%E6%96%87%E4%B8%B2/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/148216376" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/longest-palindrome-by-concatenating-two-letter-words/solutions/3686003/letmefly-2131lian-jie-liang-zi-mu-dan-ci-h5i2/" target="_blank">LeetCode题解</a>|
 |2132.用邮票贴满网格图|困难|<a href="https://leetcode.cn/problems/stamping-the-grid/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/12/14/LeetCode%202132.%E7%94%A8%E9%82%AE%E7%A5%A8%E8%B4%B4%E6%BB%A1%E7%BD%91%E6%A0%BC%E5%9B%BE/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/135002925" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/stamping-the-grid/solutions/2566644/letmefly-2132yong-you-piao-tie-man-wang-znigh/" target="_blank">LeetCode题解</a>|
 |2140.解决智力问题|中等|<a href="https://leetcode.cn/problems/solving-questions-with-brainpower/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/04/03/LeetCode%202140.%E8%A7%A3%E5%86%B3%E6%99%BA%E5%8A%9B%E9%97%AE%E9%A2%98/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/146991317" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/solving-questions-with-brainpower/solutions/3639601/letmefly-2140jie-jue-zhi-li-wen-ti-ji-yi-pxc4/" target="_blank">LeetCode题解</a>|
 |2171.拿出最少数目的魔法豆|中等|<a href="https://leetcode.cn/problems/removing-minimum-number-of-magic-beans/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2024/01/18/LeetCode%202171.%E6%8B%BF%E5%87%BA%E6%9C%80%E5%B0%91%E6%95%B0%E7%9B%AE%E7%9A%84%E9%AD%94%E6%B3%95%E8%B1%86/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/135682601" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/removing-minimum-number-of-magic-beans/solutions/2609831/letmefly-2171na-chu-zui-shao-shu-mu-de-m-jima/" target="_blank">LeetCode题解</a>|
diff --git a/Solutions/LeetCode 2131.连接两字母单词得到的最长回文串.md b/Solutions/LeetCode 2131.连接两字母单词得到的最长回文串.md
@@ -0,0 +1,203 @@
+---
+title: 2131.连接两字母单词得到的最长回文串：分类讨论(贪心)
+date: 2025-05-25 23:56:17
+tags: [题解, LeetCode, 中等, 贪心, 数组, 哈希表, 字符串, 计数, 回文, 回文串]
+categories: [题解, LeetCode]
+---
+
+# 【LetMeFly】2131.连接两字母单词得到的最长回文串：分类讨论(贪心)
+
+力扣题目链接：[https://leetcode.cn/problems/longest-palindrome-by-concatenating-two-letter-words/](https://leetcode.cn/problems/longest-palindrome-by-concatenating-two-letter-words/)
+
+<p>给你一个字符串数组&nbsp;<code>words</code>&nbsp;。<code>words</code>&nbsp;中每个元素都是一个包含 <strong>两个</strong>&nbsp;小写英文字母的单词。</p>
+
+<p>请你从 <code>words</code>&nbsp;中选择一些元素并按 <b>任意顺序</b>&nbsp;连接它们，并得到一个 <strong>尽可能长的回文串</strong>&nbsp;。每个元素 <strong>至多</strong>&nbsp;只能使用一次。</p>
+
+<p>请你返回你能得到的最长回文串的 <strong>长度</strong>&nbsp;。如果没办法得到任何一个回文串，请你返回 <code>0</code>&nbsp;。</p>
+
+<p><strong>回文串</strong>&nbsp;指的是从前往后和从后往前读一样的字符串。</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre><b>输入：</b>words = ["lc","cl","gg"]
+<b>输出：</b>6
+<b>解释：</b>一个最长的回文串为 "lc" + "gg" + "cl" = "lcggcl" ，长度为 6 。
+"clgglc" 是另一个可以得到的最长回文串。
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre><b>输入：</b>words = ["ab","ty","yt","lc","cl","ab"]
+<b>输出：</b>8
+<strong>解释：</strong>最长回文串是 "ty" + "lc" + "cl" + "yt" = "tylcclyt" ，长度为 8 。
+"lcyttycl" 是另一个可以得到的最长回文串。
+</pre>
+
+<p><strong>示例 3：</strong></p>
+
+<pre><b>输入：</b>words = ["cc","ll","xx"]
+<b>输出：</b>2
+<b>解释：</b>最长回文串是 "cc" ，长度为 2 。
+"ll" 是另一个可以得到的最长回文串。"xx" 也是。</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>1 &lt;= words.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>words[i].length == 2</code></li>
+	<li><code>words[i]</code>&nbsp;仅包含小写英文字母。</li>
+</ul>
+
+
+    
+## 解题方法：分类讨论
+
+### 解题思路
+
+有的字符串自对称(如`aa`)，有的字符串非自对称(如`ab`)。
+
+非对称的字符串只能和和它对称的字符串放到对称的位置(如`ab**ba`)，而自对称的字符串不但能和自身放到对称的位置(如`aa**aa`)也可以自身单独放到最中间的位置(如`**aa**`)。
+
+但是，在整个最终构造的字符串中，自对称放字符串放到最中间的至多只能有一个。
+
+### 具体方法
+
+使用一个哈希表或`26x26`大小的数组统计每种字符串的出现次数。
+
+使用变量`i`从`0`到`25`遍历：
+
+> 首先对于自对称的字符串(如`aa`)，假设有$n$个，则可以拿$\lfloor\frac{n}2\rfloor$对放到对称的位置。若$n$为奇数，则还可以保留一个放到最中间的位置。
+>
+> 接着使用变量`j`从`i+1`到`26`遍历，可以互相放到对称位置的字符串一共有$\min(times[i][j], times[j][i])$对。
+
+最终，由于中间位置最多只能放一对，所以$(对称对数\times2+中间个数)\times 2$即为所求。
+
+### 时空复杂度分析
+
++ 时间复杂度$O(N^2)$
++ 空间复杂度$O(N\log N)$
+
+### AC代码
+
+#### Go
+
+```go
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 23:39:17
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-25 23:54:22
+ */
+package main
+
+func longestPalindrome(words []string) int {
+    times := make([][]int, 26)
+    for i := range times {
+        times[i] = make([]int, 26)
+    }
+    for _, word := range words {
+        times[word[0] - 'a'][word[1] - 'a']++
+    }
+    side, mid := 0, 0
+    for i := range times {
+        side += times[i][i] / 2 * 2
+        mid |= times[i][i] % 2
+        for j := i + 1; j < 26; j++ {
+            side += min(times[i][j], times[j][i]) * 2
+        }
+    }
+    return (side + mid) * 2
+}
+```
+
+#### C++
+
+```cpp
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 23:39:17
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-26 00:04:19
+ */
+class Solution {
+public:
+    int longestPalindrome(vector<string>& words) {
+        int cnt[26][26] = {0};
+        for (string& word : words) {
+            cnt[word[0] - 'a'][word[1] - 'a']++;
+        }
+        int ans = 0, middle = 0;
+        for (int i = 0; i < 26; i++) {
+            ans += cnt[i][i] / 2 * 2;
+            middle |= cnt[i][i] % 2;
+            for (int j = i + 1; j < 26; j++) {
+                ans += min(cnt[i][j], cnt[j][i]) * 2;
+            }
+        }
+        return (ans + middle) * 2;
+    }
+};
+```
+
+#### Python
+
+```python
+'''
+Author: LetMeFly
+Date: 2025-05-25 23:39:17
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-05-25 23:47:11
+'''
+from typing import List
+
+class Solution:
+    def longestPalindrome(self, words: List[str]) -> int:
+        cnt = [[0] * 26 for _ in range(26)]
+        for word in words:
+            cnt[ord(word[0]) - ord('a')][ord(word[1]) - ord('a')] += 1
+        ans = middle = 0
+        for i in range(26):
+            ans += cnt[i][i] // 2 * 2
+            middle |= cnt[i][i] % 2
+            for j in range(i + 1, 26):
+                ans += min(cnt[i][j], cnt[j][i]) * 2
+        return (ans + middle) * 2
+```
+
+#### Java
+
+```java
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 23:39:17
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-25 23:51:33
+ */
+class Solution {
+    public int longestPalindrome(String[] words) {
+        int[][] times = new int[26][26];
+        for (String word : words) {
+            times[word.charAt(0) - 'a'][word.charAt(1) - 'a']++;
+        }
+        int side = 0, middle = 0;
+        for (int i = 0; i < 26; i++) {
+            side += times[i][i] / 2 * 2;
+            middle |= times[i][i] % 2;
+            for (int j = i + 1; j < 26; j++) {
+                side += Math.min(times[i][j], times[j][i]) * 2;
+            }
+        }
+        return (side + middle) * 2;
+    }
+}
+```
+
+> 同步发文于[CSDN](https://letmefly.blog.csdn.net/article/details/148216376)和我的[个人博客](https://blog.letmefly.xyz/)，原创不易，转载经作者同意后请附上[原文链接](https://blog.letmefly.xyz/2025/05/25/LeetCode%202131.%E8%BF%9E%E6%8E%A5%E4%B8%A4%E5%AD%97%E6%AF%8D%E5%8D%95%E8%AF%8D%E5%BE%97%E5%88%B0%E7%9A%84%E6%9C%80%E9%95%BF%E5%9B%9E%E6%96%87%E4%B8%B2/)哦~
+>
+> 千篇源码题解[已开源](https://github.com/LetMeFly666/LeetCode)
+
+（最近CSDN发文时咋不出默认封面图了）
diff --git a/Solutions/Other-English-LearningNotes-SomeWords.md b/Solutions/Other-English-LearningNotes-SomeWords.md
@@ -1183,6 +1183,10 @@ categories: [自用]
 |stipulate|v. 规定，明确要求<br/>adj. 有托叶的|
 |businesslike|adj. 高效的，井然有序的，工作认真而有条理的|
 |buddhism|n. 佛教|
+|||
+|arduous|adj. 艰苦的，简单的，费力的|
+|wherein|adv. 其中，在那里，在那种情况下，以什么方式<details><summary>例句</summary>He looked around the room, <font color="#28bea0">wherein</font> were assembled his entire family.<br/>他环视了下房间，他全家人都在那里。</details>|
+|handout|n. 捐赠品，救济品，传单，(发给学生的)课堂讲义|
 
 <p class="wordCounts">单词收录总数</p>
 
diff --git a/Solutions/Other-Japanese-LearningNotes.md b/Solutions/Other-Japanese-LearningNotes.md
@@ -358,6 +358,7 @@ xx型
 |静か(しずか)|安静的|
 |にぎやか|热闹的|
 |いろいろ|各种各样的|
+|カラフル(colorful)|五颜六色的|
 |じょうぶ|结实的|
 |明るい(あかるい)|明亮的|
 |暗い(くらい)|昏暗的|
@@ -403,6 +404,7 @@ xx型
 |窓(まど)|窗户|
 |カーテン|窗帘|
 |ゆか|地板|
+|カーペット|地毯|
 |冷蔵庫(れいぞうこ)|冰箱|
 |ソファ(sofa)|沙发|
 |家具(かぐ)|家具|
@@ -503,6 +505,7 @@ xx型
 |ゴミ|垃圾|
 |広告(こうこく)|广告|
 |シャンプー|洗发水|
+|アクセサリー(accessory)|配件|
 |||
 |シャツ|衬衫|
 |Tシャツ|T恤|
@@ -541,6 +544,7 @@ xx型
 |レストラン|餐馆|
 |ダイニング|餐厅|
 |食堂(しょくどう)|食堂|
+|会場(かいじょう)|会场|
 |カフェ|咖啡馆|
 |コンビニ|便利店|
 |図書館(としょかん)|图书馆|
diff --git a/toSay.md b/toSay.md
@@ -0,0 +1,9 @@
+<!--
+ * @Author: LetMeFly
+ * @Date: 2025-05-25 22:00:40
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-05-25 22:00:57
+-->
+愉快周末又要结束了
+
+周日下午一个组会直接干掉大半天
diff --git a/tryGoPy/MGJW/thisWeek/.gitignore b/tryGoPy/MGJW/thisWeek/.gitignore
@@ -0,0 +1 @@
+pics
diff --git a/tryGoPy/MGJW/thisWeek/chat.md b/tryGoPy/MGJW/thisWeek/chat.md
diff --git a/tryGoPy/MGJW/thisWeek/d.md b/tryGoPy/MGJW/thisWeek/d.md
diff --git a/tryGoPy/MGJW/thisWeek/周报.md b/tryGoPy/MGJW/thisWeek/周报.md
