update: 添加问题“2311.小于等于K的最长二进制子序列”的代码和题解(#1001)

* archive: #1000 - 晚上回去换设备 (#1000)

java - AC,83.64%,72.73%

Signed-off-by: LetMeFly666 <[email protected]>

* 2311: AC.cpp + WA.py (#1000)

cpp - AC,4.00%,64.00%

Signed-off-by: LetMeFly666 <[email protected]>

* 2311: AC.py+ WA.go (#1000)

py - AC,100.00%,45.10%

Signed-off-by: LetMeFly666 <[email protected]>

* 2311: AC.(cpp+py+go) + WA.java (#1000)

其实i<k_length的时候再判断就好，不需要等于的时候（例如k只有1个bit，那么也就i=0的时候值得判断一下）

cpp - AC,小优化,100.00%,22.22%
py - AC,29.41%,33.33%
go - AC,100.00%,88.24%

Signed-off-by: LetMeFly666 <[email protected]>

* 2311: AC.java (#1000)

java - AC,100.00%,65.71%

Signed-off-by: LetMeFly666 <[email protected]>

* update: 添加问题“2311.小于等于K的最长二进制子序列”的代码和题解(#1001)

Signed-off-by: LetMeFly666 <[email protected]>

---------

Signed-off-by: LetMeFly666 <[email protected]>

Author: LetMeFly666

.changelog

@@ -0,0 +1,27 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-06-26 22:16:30
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-06-26 22:43:01
+ */
+#if defined(_WIN32) || defined(__APPLE__)
+#include "_[1,2]toVector.h"
+#endif
+
+class Solution {
+public:
+    int longestSubsequence(string s, int k) {
+        int ans = 0, val = 0, k_length = 32 - __builtin_clz(k), n = s.size();  // k=0时k_length=0计算错误也不受影响
+        for (int i = 0; i < n; i++) {
+            if (s[n - i - 1] == '0') {
+                ans++;
+                continue;
+            }
+            if (i < k_length && val + (1 << i) <= k) {
+                val += 1 << i;
+                ans++;
+            }
+        }
+        return ans;
+    }
+};

Codes/2311-longest-binary-subsequence-less-than-or-equal-to-k.cpp

@@ -0,0 +1,24 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-06-26 22:16:30
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-06-26 22:39:55
+ */
+package main
+
+import "math/bits"
+
+func longestSubsequence(s string, k int) (ans int) {
+    val, n, lenK := 0, len(s), bits.Len(uint(k))
+    for i := 0; i < n; i++ {
+        if s[n - i - 1] == '0' {
+            ans++
+            continue
+        }
+        if i < lenK && val + (1 << i) <= k {
+            ans++
+            val += 1 << i
+        }
+    }
+    return
+}

Codes/2311-longest-binary-subsequence-less-than-or-equal-to-k.go

@@ -0,0 +1,22 @@
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-06-26 22:16:30
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-06-26 22:45:37
+ */
+class Solution {
+    public int longestSubsequence(String s, int k) {
+        int ans = 0, n = s.length(), lenK = 32 - Integer.numberOfLeadingZeros(k), val = 0;
+        for (int i = 0; i < n; i++) {
+            if (s.charAt(n - i - 1) == '0') {
+                ans++;
+                continue;
+            }
+            if (i < lenK && val + (1 << i) <= k) {
+                val += 1 << i;
+                ans++;
+            }
+        }
+        return ans;
+    }
+}

Codes/2311-longest-binary-subsequence-less-than-or-equal-to-k.java

@@ -0,0 +1,17 @@
+'''
+Author: LetMeFly
+Date: 2025-06-26 22:16:30
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-06-26 22:38:54
+'''
+class Solution:
+    def longestSubsequence(self, s: str, k: int) -> int:
+        ans, val, k_length = 0, 0, k.bit_length()
+        for i, c in enumerate(s[::-1]):
+            if c == '0':
+                ans += 1
+                continue
+            if i < k_length and val + (1 << i) <= k:
+                ans += 1
+                val += 1 << i
+        return ans

Codes/2311-longest-binary-subsequence-less-than-or-equal-to-k.py

@@ -121,7 +121,7 @@
 |Python - with语句 - 写一个支持with方法调用的类|<a href="https://blog.letmefly.xyz/2024/05/08/Other-Python-WithStatement-write1classSupportingWith/">本平台博客</a>|<a href="https://letmefly.blog.csdn.net/article/details/138576722">CSDN博客</a>|
 |QT - 实例 - 可点击的进度条、无窗口应用|<a href="https://blog.letmefly.xyz/2023/08/02/Other-QT-Example-ClickableProgressBar-noWindow/">本平台博客</a>|无|
 |北邮暑期课 - R语言数据分析|<a href="https://blog.letmefly.xyz/2023/06/26/Other-RLanguageDataAnalysis">本平台博客</a>|无|
-|域名转到国外注册商-备案实效风险折腾日记|<a href="https://blog.letmefly.xyz/2025/06/23/Other-Server-BeiAnXiaoTuCao/">本平台博客</a>|<a href="https://letmefly.blog.csdn.net/article/details/148844350">CSDN博客</a>|
+|域名转到国外注册商-备案失效风险折腾日记|<a href="https://blog.letmefly.xyz/2025/06/23/Other-Server-BeiAnXiaoTuCao/">本平台博客</a>|<a href="https://letmefly.blog.csdn.net/article/details/148844350">CSDN博客</a>|
 |SVG(可缩放矢量图形) - toLearn 和 创建|<a href="https://blog.letmefly.xyz/2023/07/06/Other-SVG-ToLearnAndToCreate/">本平台博客</a>|无|
 |Verilog学习笔记 - 极简极入门级|<a href="https://blog.letmefly.xyz/2023/01/06/Other-Verilog-Note/">本平台博客</a>|<a href="https://letmefly.blog.csdn.net/article/details/128584160">CSDN博客</a>|
 |Cloudflare Warp+，1.1.1.1，如何使用，如何获取免费流量，如何优选IP|<a href="https://blog.letmefly.xyz/2023/08/25/Other-VPN-CloudflareWarp+1.1.1.1">本平台博客</a>|无|
@@ -724,6 +724,7 @@
 |2303.计算应缴税款总额|简单|<a href="https://leetcode.cn/problems/calculate-amount-paid-in-taxes/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/01/23/LeetCode%202303.%E8%AE%A1%E7%AE%97%E5%BA%94%E7%BC%B4%E7%A8%8E%E6%AC%BE%E6%80%BB%E9%A2%9D/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/128751683" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/calculate-amount-paid-in-taxes/solutions/2073612/letmefly-2303ji-suan-ying-jiao-shui-kuan-lzsi/" target="_blank">LeetCode题解</a>|
 |2304.网格中的最小路径代价|中等|<a href="https://leetcode.cn/problems/minimum-path-cost-in-a-grid/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/11/22/LeetCode%202304.%E7%BD%91%E6%A0%BC%E4%B8%AD%E7%9A%84%E6%9C%80%E5%B0%8F%E8%B7%AF%E5%BE%84%E4%BB%A3%E4%BB%B7/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/134563145" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/minimum-path-cost-in-a-grid/solutions/2537837/letmefly-2304wang-ge-zhong-de-zui-xiao-l-bjad/" target="_blank">LeetCode题解</a>|
 |2309.兼具大小写的最好英文字母|简单|<a href="https://leetcode.cn/problems/greatest-english-letter-in-upper-and-lower-case/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/01/27/LeetCode%202309.%E5%85%BC%E5%85%B7%E5%A4%A7%E5%B0%8F%E5%86%99%E7%9A%84%E6%9C%80%E5%A5%BD%E8%8B%B1%E6%96%87%E5%AD%97%E6%AF%8D/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/128769360" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/greatest-english-letter-in-upper-and-lower-case/solutions/2077745/letmefly-2309jian-ju-da-xiao-xie-de-zui-3hgag/" target="_blank">LeetCode题解</a>|
+|2311.小于等于K的最长二进制子序列|中等|<a href="https://leetcode.cn/problems/longest-binary-subsequence-less-than-or-equal-to-k/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2025/06/26/LeetCode%202311.%E5%B0%8F%E4%BA%8E%E7%AD%89%E4%BA%8EK%E7%9A%84%E6%9C%80%E9%95%BF%E4%BA%8C%E8%BF%9B%E5%88%B6%E5%AD%90%E5%BA%8F%E5%88%97/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/148935308" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/longest-binary-subsequence-less-than-or-equal-to-k/solutions/3709306/letmefly-2311xiao-yu-deng-yu-k-de-zui-ch-2n27/" target="_blank">LeetCode题解</a>|
 |2312.卖木头块|困难|<a href="https://leetcode.cn/problems/selling-pieces-of-wood/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2024/03/15/LeetCode%202312.%E5%8D%96%E6%9C%A8%E5%A4%B4%E5%9D%97/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/136747100" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/selling-pieces-of-wood/solutions/2689067/letmefly-2312mai-mu-tou-kuai-dong-tai-gu-vk5a/" target="_blank">LeetCode题解</a>|
 |2316.统计无向图中无法互相到达点对数|中等|<a href="https://leetcode.cn/problems/count-unreachable-pairs-of-nodes-in-an-undirected-graph/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/10/21/LeetCode%202316.%E7%BB%9F%E8%AE%A1%E6%97%A0%E5%90%91%E5%9B%BE%E4%B8%AD%E6%97%A0%E6%B3%95%E4%BA%92%E7%9B%B8%E5%88%B0%E8%BE%BE%E7%82%B9%E5%AF%B9%E6%95%B0/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/133962709" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/count-unreachable-pairs-of-nodes-in-an-undirected-graph/solutions/2492186/letmefly-2316tong-ji-wu-xiang-tu-zhong-w-79vz/" target="_blank">LeetCode题解</a>|
 |2335.装满杯子需要的最短总时长|简单|<a href="https://leetcode.cn/problems/minimum-amount-of-time-to-fill-cups/" target="_blank">题目地址</a>|<a href="https://blog.letmefly.xyz/2023/02/11/LeetCode%202335.%E8%A3%85%E6%BB%A1%E6%9D%AF%E5%AD%90%E9%9C%80%E8%A6%81%E7%9A%84%E6%9C%80%E7%9F%AD%E6%80%BB%E6%97%B6%E9%95%BF/" target="_blank">题解地址</a>|<a href="https://letmefly.blog.csdn.net/article/details/128980819" target="_blank">CSDN题解</a>|<a href="https://leetcode.cn/problems/minimum-amount-of-time-to-fill-cups/solutions/2105156/letmefly-2335zhuang-man-bei-zi-xu-yao-de-kq65/" target="_blank">LeetCode题解</a>|

README.md

@@ -0,0 +1,180 @@
+---
+title: 2311.小于等于 K 的最长二进制子序列：贪心（先选0再选1）-好像还是比灵神写的清晰些
+date: 2025-06-26 22:46:22
+tags: [题解, LeetCode, 中等, 贪心, 字符串, 位运算]
+categories: [题解, LeetCode]
+---
+
+# 【LetMeFly】2311.小于等于 K 的最长二进制子序列：贪心（先选0再选1）-好像还是比灵神写的清晰些
+
+力扣题目链接：[https://leetcode.cn/problems/longest-binary-subsequence-less-than-or-equal-to-k/](https://leetcode.cn/problems/longest-binary-subsequence-less-than-or-equal-to-k/)
+
+<p>给你一个二进制字符串&nbsp;<code>s</code>&nbsp;和一个正整数&nbsp;<code>k</code>&nbsp;。</p>
+
+<p>请你返回 <code>s</code>&nbsp;的 <strong>最长</strong>&nbsp;子序列，且该子序列对应的 <strong>二进制</strong>&nbsp;数字小于等于 <code>k</code>&nbsp;。</p>
+
+<p>注意：</p>
+
+<ul>
+	<li>子序列可以有 <strong>前导 0</strong>&nbsp;。</li>
+	<li>空字符串视为&nbsp;<code>0</code>&nbsp;。</li>
+	<li><strong>子序列</strong>&nbsp;是指从一个字符串中删除零个或者多个字符后，不改变顺序得到的剩余字符序列。</li>
+</ul>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre><b>输入：</b>s = "1001010", k = 5
+<b>输出：</b>5
+<b>解释：</b>s 中小于等于 5 的最长子序列是 "00010" ，对应的十进制数字是 2 。
+注意 "00100" 和 "00101" 也是可行的最长子序列，十进制分别对应 4 和 5 。
+最长子序列的长度为 5 ，所以返回 5 。
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre><b>输入：</b>s = "00101001", k = 1
+<b>输出：</b>6
+<b>解释：</b>"000001" 是 s 中小于等于 1 的最长子序列，对应的十进制数字是 1 。
+最长子序列的长度为 6 ，所以返回 6 。
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
+	<li><code>s[i]</code> 要么是&nbsp;<code>'0'</code>&nbsp;，要么是&nbsp;<code>'1'</code> 。</li>
+	<li><code>1 &lt;= k &lt;= 10<sup>9</sup></code></li>
+</ul>
+
+
+    
+## 解题方法：贪心
+
+二话不说选中所有0，接着从右往左开始选1，全程保证所选元素不超过$k$。
+
+Why?
+
+选1可能导致没法选后面的0，选0不会影响后面的选择。如果选1导致无法选后面的0，那么不如舍弃这个1直接替换成0。综上**先选0更优**。
+
+选1好说，当然是**从低位往高位选1**啦。
+
++ 时间复杂度$O(len(s))$
++ 空间复杂度$O(1)$
+
+### AC代码
+
+#### C++
+
+```cpp
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-06-26 22:16:30
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-06-26 22:43:01
+ */
+class Solution {
+public:
+    int longestSubsequence(string s, int k) {
+        int ans = 0, val = 0, k_length = 32 - __builtin_clz(k), n = s.size();  // k=0时k_length=0计算错误也不受影响
+        for (int i = 0; i < n; i++) {
+            if (s[n - i - 1] == '0') {
+                ans++;
+                continue;
+            }
+            if (i < k_length && val + (1 << i) <= k) {
+                val += 1 << i;
+                ans++;
+            }
+        }
+        return ans;
+    }
+};
+```
+
+#### Python
+
+```python
+'''
+Author: LetMeFly
+Date: 2025-06-26 22:16:30
+LastEditors: LetMeFly.xyz
+LastEditTime: 2025-06-26 22:38:54
+'''
+class Solution:
+    def longestSubsequence(self, s: str, k: int) -> int:
+        ans, val, k_length = 0, 0, k.bit_length()
+        for i, c in enumerate(s[::-1]):
+            if c == '0':
+                ans += 1
+                continue
+            if i < k_length and val + (1 << i) <= k:
+                ans += 1
+                val += 1 << i
+        return ans
+```
+
+Python也可以理解为[依次删除左边1直到int(s)<=k](https://leetcode.cn/problems/longest-binary-subsequence-less-than-or-equal-to-k/solutions/3701151/xiao-yu-deng-yu-k-de-zui-chang-er-jin-zh-7vk8/comments/3064179/)。
+
+#### Java
+
+```java
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-06-26 22:16:30
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-06-26 22:45:37
+ */
+class Solution {
+    public int longestSubsequence(String s, int k) {
+        int ans = 0, n = s.length(), lenK = 32 - Integer.numberOfLeadingZeros(k), val = 0;
+        for (int i = 0; i < n; i++) {
+            if (s.charAt(n - i - 1) == '0') {
+                ans++;
+                continue;
+            }
+            if (i < lenK && val + (1 << i) <= k) {
+                val += 1 << i;
+                ans++;
+            }
+        }
+        return ans;
+    }
+}
+```
+
+#### Go
+
+```go
+/*
+ * @Author: LetMeFly
+ * @Date: 2025-06-26 22:16:30
+ * @LastEditors: LetMeFly.xyz
+ * @LastEditTime: 2025-06-26 22:39:55
+ */
+package main
+
+import "math/bits"
+
+func longestSubsequence(s string, k int) (ans int) {
+    val, n, lenK := 0, len(s), bits.Len(uint(k))
+    for i := 0; i < n; i++ {
+        if s[n - i - 1] == '0' {
+            ans++
+            continue
+        }
+        if i < lenK && val + (1 << i) <= k {
+            ans++
+            val += 1 << i
+        }
+    }
+    return
+}
+```
+
+> 同步发文于[CSDN](https://letmefly.blog.csdn.net/article/details/148935308)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/2025/06/26/LeetCode%202311.%E5%B0%8F%E4%BA%8E%E7%AD%89%E4%BA%8EK%E7%9A%84%E6%9C%80%E9%95%BF%E4%BA%8C%E8%BF%9B%E5%88%B6%E5%AD%90%E5%BA%8F%E5%88%97/)哦~
+>
+> 千篇源码题解[已开源](https://github.com/LetMeFly666/LeetCode)