update: 添加问题“1292.元素和小于等于阈值的正方形的最大边长”的代码和题解 (#1335)

* en: 2026.1.19

* 1292: AC.cpp (#1334) - AC,91.34%,58.44% 一遍过了

* update: 添加问题“1292.元素和小于等于阈值的正方形的最大边长”的代码和题解 (#1335)

Signed-off-by: LetMeFly666 <Tisfy@qq.com>

---------

Signed-off-by: LetMeFly666 <Tisfy@qq.com>

Author: LetMeFly666

.commitTitleExtra

@@ -0,0 +1,32 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2026-01-19 21:47:34
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2026-01-19 21:55:16
+ */
+#if defined(_WIN32) || defined(__APPLE__)
+#include "_[1,2]toVector.h"
+#endif
+
+class Solution {
+public:
+    int maxSideLength(vector<vector<int>>& mat, int threshold) {
+        int n = mat.size(), m = mat[0].size();
+        vector<vector<int>> prefix(n + 1, vector<int>(m + 1));
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                prefix[i + 1][j + 1] = mat[i][j] - prefix[i][j] + prefix[i][j + 1] + prefix[i + 1][j];
+            }
+        }
+
+        int ans = 0;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                while (i + ans < n && j + ans < m && prefix[i + ans + 1][j + ans + 1] - prefix[i + ans + 1][j] - prefix[i][j + ans + 1] + prefix[i][j] <= threshold) {
+                    ans++;
+                }
+            }
+        }
+        return ans;
+    }
+};

.commitmsg

@@ -2,13 +2,12 @@
  * @Author: LetMeFly
  * @Date: 2026-01-18 20:47:19
  * @LastEditors: LetMeFly.xyz
- * @LastEditTime: 2026-01-18 23:16:07
+ * @LastEditTime: 2026-01-18 23:17:50
  */
 #if defined(_WIN32) || defined(__APPLE__)
 #include "_[1,2]toVector.h"
 #endif
 
-// THIS CANNOT BE ACCEPTED
 class Solution {
 private:
     vector<vector<int>> rowSum, colSum;
@@ -17,7 +16,7 @@ class Solution {
         int cnt = 0, cntRev = 0;
         for (int i = 0; i < l; i++) {
             cnt += grid[x + i][y + i];
-            cntRev += grid[x + l - i - 1][y + l - i - 1];
+            cntRev += grid[x + i][y + l - i - 1];  // 易错
         }
         if (cnt != cntRev) {
             return false;

Codes/1292-maximum-side-length-of-a-square-with-sum-less-than-or-equal-to-threshold.cpp

@@ -542,6 +542,7 @@
 |1287.有序数组中出现次数超过25%的元素|简单|<a href="https://leetcode.cn/problems/element-appearing-more-than-25-in-sorted-array/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/02/17/LeetCode%201287.%E6%9C%89%E5%BA%8F%E6%95%B0%E7%BB%84%E4%B8%AD%E5%87%BA%E7%8E%B0%E6%AC%A1%E6%95%B0%E8%B6%85%E8%BF%8725%E7%9A%84%E5%85%83%E7%B4%A0" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/145683090" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/element-appearing-more-than-25-in-sorted-array/solutions/3078136/letmefly-1287you-xu-shu-zu-zhong-chu-xia-wdat/" target="_blank">LeetCode题解</a>|
 |1289.下降路径最小和II|困难|<a href="https://leetcode.cn/problems/minimum-falling-path-sum-ii/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/08/10/LeetCode%201289.%E4%B8%8B%E9%99%8D%E8%B7%AF%E5%BE%84%E6%9C%80%E5%B0%8F%E5%92%8CII/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/132201281" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/minimum-falling-path-sum-ii/solutions/2381173/letmefly-1289xia-jiang-lu-jing-zui-xiao-kt8cj/" target="_blank">LeetCode题解</a>|
 |1290.二进制链表转整数|简单|<a href="https://leetcode.cn/problems/convert-binary-number-in-a-linked-list-to-integer/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/07/14/LeetCode%201290.%E4%BA%8C%E8%BF%9B%E5%88%B6%E9%93%BE%E8%A1%A8%E8%BD%AC%E6%95%B4%E6%95%B0/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/149342077" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/convert-binary-number-in-a-linked-list-to-integer/solutions/3723954/letmefly-1290er-jin-zhi-lian-biao-zhuan-adolg/" target="_blank">LeetCode题解</a>|
+|1292.元素和小于等于阈值的正方形的最大边长|中等|<a href="https://leetcode.cn/problems/maximum-side-length-of-a-square-with-sum-less-than-or-equal-to-threshold/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2026/01/19/LeetCode%201292.%E5%85%83%E7%B4%A0%E5%92%8C%E5%B0%8F%E4%BA%8E%E7%AD%89%E4%BA%8E%E9%98%88%E5%80%BC%E7%9A%84%E6%AD%A3%E6%96%B9%E5%BD%A2%E7%9A%84%E6%9C%80%E5%A4%A7%E8%BE%B9%E9%95%BF/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/157145833" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/maximum-side-length-of-a-square-with-sum-less-than-or-equal-to-threshold/solutions/3884572/letmefly-1292yuan-su-he-xiao-yu-deng-yu-4220r/" target="_blank">LeetCode题解</a>|
 |1295.统计位数为偶数的数字|简单|<a href="https://leetcode.cn/problems/find-numbers-with-even-number-of-digits/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/04/30/LeetCode%201295.%E7%BB%9F%E8%AE%A1%E4%BD%8D%E6%95%B0%E4%B8%BA%E5%81%B6%E6%95%B0%E7%9A%84%E6%95%B0%E5%AD%97/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/147637587" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/find-numbers-with-even-number-of-digits/solutions/3666390/letmefly-1295tong-ji-wei-shu-wei-ou-shu-bwhfr/" target="_blank">LeetCode题解</a>|
 |1299.将每个元素替换为右侧最大元素|简单|<a href="https://leetcode.cn/problems/replace-elements-with-greatest-element-on-right-side/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/02/16/LeetCode%201299.%E5%B0%86%E6%AF%8F%E4%B8%AA%E5%85%83%E7%B4%A0%E6%9B%BF%E6%8D%A2%E4%B8%BA%E5%8F%B3%E4%BE%A7%E6%9C%80%E5%A4%A7%E5%85%83%E7%B4%A0/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/145661909" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/replace-elements-with-greatest-element-on-right-side/solutions/3076497/letmefly-1299jiang-mei-ge-yuan-su-ti-hua-4y58/" target="_blank">LeetCode题解</a>|
 |1302.层数最深叶子节点的和|中等|<a href="https://leetcode.cn/problems/deepest-leaves-sum/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2022/08/17/LeetCode%201302.%E5%B1%82%E6%95%B0%E6%9C%80%E6%B7%B1%E5%8F%B6%E5%AD%90%E8%8A%82%E7%82%B9%E7%9A%84%E5%92%8C/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/126377912" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/deepest-leaves-sum/solution/letmefly-1302ceng-shu-zui-shen-xie-zi-ji-eyu0/" target="_blank">LeetCode题解</a>|

Codes/1895-largest-magic-square.cpp

@@ -0,0 +1,107 @@
+---
+title: 1292.元素和小于等于阈值的正方形的最大边长：二维前缀和（无需二分）+抽象速懂的描述
+date: 2026-01-19 23:27:08
+tags: [题解, LeetCode, 中等, 数组, 矩阵, 前缀和]
+categories: [题解, LeetCode]
+index_img: https://assets.leetcode.cn/aliyun-lc-upload/uploads/2019/12/15/e1.png
+---
+
+# 【LetMeFly】1292.元素和小于等于阈值的正方形的最大边长：二维前缀和（无需二分）+抽象速懂的描述
+
+力扣题目链接：[https://leetcode.cn/problems/maximum-side-length-of-a-square-with-sum-less-than-or-equal-to-threshold/](https://leetcode.cn/problems/maximum-side-length-of-a-square-with-sum-less-than-or-equal-to-threshold/)
+
+<p>给你一个大小为&nbsp;<code>m x n</code>&nbsp;的矩阵&nbsp;<code>mat</code>&nbsp;和一个整数阈值&nbsp;<code>threshold</code>。</p>
+
+<p>请你返回元素总和小于或等于阈值的正方形区域的最大边长；如果没有这样的正方形区域，则返回 <strong>0&nbsp;</strong>。<br />
+&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.cn/aliyun-lc-upload/uploads/2019/12/15/e1.png" style="height: 186px; width: 335px;" /></p>
+
+<pre>
+<strong>输入：</strong>mat = [[1,1,3,2,4,3,2],[1,1,3,2,4,3,2],[1,1,3,2,4,3,2]], threshold = 4
+<strong>输出：</strong>2
+<strong>解释：</strong>总和小于或等于 4 的正方形的最大边长为 2，如图所示。
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<strong>输入：</strong>mat = [[2,2,2,2,2],[2,2,2,2,2],[2,2,2,2,2],[2,2,2,2,2],[2,2,2,2,2]], threshold = 1
+<strong>输出：</strong>0
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>m == mat.length</code></li>
+	<li><code>n == mat[i].length</code></li>
+	<li><code>1 &lt;= m, n &lt;= 300</code></li>
+	<li><code>0 &lt;= mat[i][j] &lt;= 10<sup>4</sup></code></li>
+	<li><code>0 &lt;= threshold &lt;= 10<sup>5</sup></code><sup>&nbsp;</sup></li>
+</ul>
+
+
+    
+## 解题方法：前缀和
+
+二维矩阵的二维前缀和可以快速计算出某个子矩阵的元素和。
+
+```
+AB
+CD
+```
+
+其中`prefix[D]`代表从左上角到`D`这个矩阵的元素和，计算方法为`D+B+C-A`。
+
+```
+ABC
+DEF
+GHI
+```
+
+那么想计算`EFHI`这个子矩阵的元素和就只需要`prefix[I]-prefix[C]-prefix[G]+prefix[A]`。
+
+二层循环枚举矩阵左上角顶点，使用一个变量`ans`作为答案合法边长并且**只增不减**，那么二层循环时间复杂度$O(mn)$，内层`ans`总时间复杂度不会超过$O\min(m,n)$。
+
++ 时间复杂度$O(mn)$
++ 空间复杂度$O(N\log N)$
+
+### AC代码
+
+#### C++
+
+```cpp
+/*
+ * @LastEditTime: 2026-01-19 21:55:16
+ */
+class Solution {
+public:
+    int maxSideLength(vector<vector<int>>& mat, int threshold) {
+        int n = mat.size(), m = mat[0].size();
+        vector<vector<int>> prefix(n + 1, vector<int>(m + 1));
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                prefix[i + 1][j + 1] = mat[i][j] - prefix[i][j] + prefix[i][j + 1] + prefix[i + 1][j];
+            }
+        }
+
+        int ans = 0;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                while (i + ans < n && j + ans < m && prefix[i + ans + 1][j + ans + 1] - prefix[i + ans + 1][j] - prefix[i][j + ans + 1] + prefix[i][j] <= threshold) {
+                    ans++;
+                }
+            }
+        }
+        return ans;
+    }
+};
+```
+
+> 同步发文于[CSDN](https://letmefly.blog.csdn.net/article/details/157145833)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/2026/01/19/LeetCode%201292.%E5%85%83%E7%B4%A0%E5%92%8C%E5%B0%8F%E4%BA%8E%E7%AD%89%E4%BA%8E%E9%98%88%E5%80%BC%E7%9A%84%E6%AD%A3%E6%96%B9%E5%BD%A2%E7%9A%84%E6%9C%80%E5%A4%A7%E8%BE%B9%E9%95%BF/)哦~
+>
+> 千篇源码题解[已开源](https://github.com/LetMeFly666/LeetCode)

Codes/1895-largest-magic-square_AC.cpp

@@ -385,7 +385,7 @@ Interpreter: /bin/bash
 
 ### zsh里面 path和PATH是一个
 
-ZSH中修改$path$变量也会自动修改$PATH$变量。
+ZSH中修改`$path`变量也会自动修改`$PATH`变量。
 
 ### Linux登录欢迎语motd
 
@@ -648,7 +648,7 @@ f35b2f66-3e03-4c9d-80b5-d72059a8735d
 1. 固件支持WOL
 2. 局域网或公网可达
 3. 网卡有待机电
-4. 接收到魔术网络包(Magic Packe)，内容`6 字节的 FF`+`目标网卡 MAC 地址 × 16 次`
+4. 接收到魔术网络包(Magic Packet)，内容`6 字节的 FF`+`目标网卡 MAC 地址 × 16 次`
 
 没有认证，知道Mac地址就能发。
 

README.md

@@ -1746,6 +1746,9 @@ categories: [自用]
 |||
 |bureau|n. 局，处，科|
 |disintegration|n. 崩解，瓦解，裂变|
+|||
+|reconnaissance|n. 侦察|
+|illegible|adj. 难以辨认的，无法辨识的，字迹模糊的|
 
 + 这个web要是能设计得可以闭眼(完全不睁眼)键盘控制背单词就好了。
 + 也许可以加个AI用最近词编故事功能(返回接口中支持标注所使用单词高亮?)

Solutions/LeetCode 1292.元素和小于等于阈值的正方形的最大边长.md

@@ -0,0 +1,7 @@
+<!--
+ * @Author: LetMeFly
+ * @Date: 2026-01-18 23:44:01
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2026-01-19 21:45:08
+-->
+曝腾讯向GitHub发函，要求下架“用户可获取自己聊天记录”的仓库