一刷516

Author: diguage

README.adoc

@@ -3638,13 +3638,13 @@ TIP: **公众号的微信号是: `jikerizhi`**。__因为众所周知的原因
 |Medium
 |层序遍历
 
-//|{counter:codes}
-//|{leetcode_base_url}/longest-palindromic-subsequence/[516. Longest Palindromic Subsequence^]
-//|{source_base_url}/_0516_LongestPalindromicSubsequence.java[Java]
-//|{doc_base_url}/0516-longest-palindromic-subsequence.adoc[题解]
-//|Medium
-//|
-//
+|{counter:codes}
+|{leetcode_base_url}/longest-palindromic-subsequence/[516. Longest Palindromic Subsequence^]
+|{source_base_url}/_0516_LongestPalindromicSubsequence.java[Java]
+|{doc_base_url}/0516-longest-palindromic-subsequence.adoc[题解]
+|Medium
+|
+
 //|{counter:codes}
 //|{leetcode_base_url}/super-washing-machines/[517. Super Washing Machines^]
 //|{source_base_url}/_0517_SuperWashingMachines.java[Java]

docs/0516-longest-palindromic-subsequence.adoc

@@ -1,44 +1,68 @@
 [#0516-longest-palindromic-subsequence]
-= 516. Longest Palindromic Subsequence
+= 516. 最长回文子序列
 
-{leetcode}/problems/longest-palindromic-subsequence/[LeetCode - Longest Palindromic Subsequence^]
+https://leetcode.cn/problems/longest-palindromic-subsequence/[LeetCode - 516. 最长回文子序列 ^]
 
+给你一个字符串 `s` ，找出其中最长的回文子序列，并返回该序列的长度。
 
-Given a string s, find the longest palindromic subsequence's length in s. You may assume that the maximum length of s is 1000.
+子序列定义为：不改变剩余字符顺序的情况下，删除某些字符或者不删除任何字符形成的一个序列。
 
+*示例 1：*
 
-*Example 1:*
-Input: 
-[subs="verbatim,quotes,macros"]
-----
-"bbbab"
-----
-Output: 
-[subs="verbatim,quotes,macros"]
-----
-4
-----
-One possible longest palindromic subsequence is "bbbb".
+....
+输入：s = "bbbab"
+输出：4
+解释：一个可能的最长回文子序列为 "bbbb" 。
+....
 
+*示例 2：*
 
-*Example 2:*
-Input:
-[subs="verbatim,quotes,macros"]
-----
-"cbbd"
-----
-Output:
-[subs="verbatim,quotes,macros"]
-----
-2
-----
-One possible longest palindromic subsequence is "bb".
+....
+输入：s = "cbbd"
+输出：2
+解释：一个可能的最长回文子序列为 "bb" 。
+....
+
+*提示：*
 
+* `+1 <= s.length <= 1000+`
+* `s` 仅由小写英文字母组成
 
 
+== 思路分析
+
+在推演转移方程时，一个很大的误区是从 `dp` 矩阵视角去看。因为这是处理字符串，从一维字符串字符坐标去看，会更加清楚明了。如下图：
+
+image::images/0516-01.png[{image_attr}]
+
+根据代码流程来看，整个处理流程是从字符串的右边向左处理，相当于在“结尾”中寻找回文子串。所以，相关遍历只涉及的矩阵的左上方一半，从最下一行向上，逐行遍历。
+
 [[src-0516]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0516_LongestPalindromicSubsequence.java[tag=answer]
 ----
+--
+
+// 二刷::
+// +
+// --
+// [{java_src_attr}]
+// ----
+// include::{sourcedir}/_0516_LongestPalindromicSubsequence_2.java[tag=answer]
+// ----
+// --
+====
+
+
+== 参考资料
+
+. https://leetcode.cn/problems/longest-palindromic-subsequence/solutions/930442/zui-chang-hui-wen-zi-xu-lie-by-leetcode-hcjqp/[516. 最长回文子序列 - 官方题解^]
+. https://leetcode.cn/problems/longest-palindromic-subsequence/solutions/15118/dong-tai-gui-hua-si-yao-su-by-a380922457-3/comments/230465/[516. 最长回文子序列 - 动态规划，四要素^] -- 该评论详细解释了如何处理奇偶回文的。
+
 

docs/images/0516-01.png

@@ -1114,7 +1114,7 @@ include::0513-find-bottom-left-tree-value.adoc[leveloffset=+1]
 
 include::0515-find-largest-value-in-each-tree-row.adoc[leveloffset=+1]
 
-// include::0516-longest-palindromic-subsequence.adoc[leveloffset=+1]
+include::0516-longest-palindromic-subsequence.adoc[leveloffset=+1]
 
 // include::0517-super-washing-machines.adoc[leveloffset=+1]
 

docs/index.adoc

@@ -350,6 +350,11 @@ endif::[]
 |{doc_base_url}/0140-word-break-ii.adoc[题解]
 |✅ 回溯。没想到从 `LinkedList` 切换到 `ArrayList`，内存占用就大幅下降 43.77% → 91.82%。没有使用备忘录耗时已经击败了 98.49%。
 
+|{counter:codes2503}
+|{leetcode_base_url}/longest-palindromic-subsequence/[516. 最长回文子序列^]
+|{doc_base_url}/0516-longest-palindromic-subsequence.adoc[题解]
+|❌ 动态规划。相当于在“结尾”中寻找回文子串。从一维字符串字符坐标去看转移方程，会更加清楚明了。
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

logbook/202503.adoc

@@ -10,6 +10,10 @@
  */
 public class _0515_FindLargestValueInEachTreeRow {
   // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2024-06-25 15:32:45
+   */
   public List<Integer> largestValues(TreeNode root) {
     if (root == null) {
       return Collections.emptyList();

src/main/java/com/diguage/algo/leetcode/_0515_FindLargestValueInEachTreeRow.java

@@ -0,0 +1,30 @@
+package com.diguage.algo.leetcode;
+
+public class _0516_LongestPalindromicSubsequence {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-19 21:32:01
+   */
+  public int longestPalindromeSubseq(String s) {
+    int length = s.length();
+    int[][] dp = new int[length][length];
+    for (int i = length - 1; i >= 0; i--) {
+      dp[i][i] = 1;
+      char ic = s.charAt(i);
+      for (int j = i + 1; j < length; j++) {
+        char jc = s.charAt(j);
+        if (ic == jc) {
+          dp[i][j] = dp[i + 1][j - 1] + 2;
+        } else {
+          dp[i][j] = Math.max(dp[i + 1][j], dp[i][j - 1]);
+        }
+      }
+    }
+    return dp[0][length - 1];
+  }
+  // end::answer[]
+  public static void main(String[] args) {
+    new _0516_LongestPalindromicSubsequence().longestPalindromeSubseq("ababa");
+  }
+}