一刷873

Author: diguage

README.adoc

@@ -6136,13 +6136,13 @@ TIP: **公众号的微信号是: `jikerizhi`**。__因为众所周知的原因
 |Easy
 |
 
-//|{counter:codes}
-//|{leetcode_base_url}/length-of-longest-fibonacci-subsequence/[873. Length of Longest Fibonacci Subsequence^]
-//|{source_base_url}/_0873_LengthOfLongestFibonacciSubsequence.java[Java]
-//|{doc_base_url}/0873-length-of-longest-fibonacci-subsequence.adoc[题解]
-//|Medium
-//|
-//
+|{counter:codes}
+|{leetcode_base_url}/length-of-longest-fibonacci-subsequence/[873. Length of Longest Fibonacci Subsequence^]
+|{source_base_url}/_0873_LengthOfLongestFibonacciSubsequence.java[Java]
+|{doc_base_url}/0873-length-of-longest-fibonacci-subsequence.adoc[题解]
+|Medium
+|
+
 //|{counter:codes}
 //|{leetcode_base_url}/walking-robot-simulation/[874. Walking Robot Simulation^]
 //|{source_base_url}/_0874_WalkingRobotSimulation.java[Java]

docs/0873-length-of-longest-fibonacci-subsequence.adoc

@@ -1,60 +1,70 @@
 [#0873-length-of-longest-fibonacci-subsequence]
-= 873. Length of Longest Fibonacci Subsequence
+= 873. 最长的斐波那契子序列的长度
 
-{leetcode}/problems/length-of-longest-fibonacci-subsequence/[LeetCode - Length of Longest Fibonacci Subsequence^]
-
-A sequence `X_1, X_2, ..., X_n` is _fibonacci-like_ if:
+https://leetcode.cn/problems/length-of-longest-fibonacci-subsequence/[LeetCode - 873. 最长的斐波那契子序列的长度^]
 
+如果序列 `X~1~, X~2~, ..., X~n~` 满足下列条件，就说它是 __斐波那契式 __ 的：
 
 * `n >= 3`
-* `X_i + X_{i+1} = X_{i+2}` for all `i + 2 <= n`
-
-
-Given a *strictly increasing* array `A` of positive integers forming a sequence, find the *length* of the longest fibonacci-like subsequence of `A`.  If one does not exist, return 0.
-
-(_Recall that a subsequence is derived from another sequence `A` by deleting any number of elements (including none) from `A`, without changing the order of the remaining elements.  For example, `[3, 5, 8]` is a subsequence of `[3, 4, 5, 6, 7, 8]`._)
-
- 
-
-
+* 对于所有 `i + 2 \<= n`，都有 `X~i~ + X~i+1~ = X~i+2~`
 
+给定一个**严格递增**的正整数数组形成序列 arr，找到 arr 中最长的斐波那契式的子序列的长度。如果一个不存在，返回  0 。
 
-*Example 1:*
+_（回想一下，子序列是从原序列 arr 中派生出来的，它从 arr 中删掉任意数量的元素（也可以不删），而不改变其余元素的顺序。例如， `[3, 5, 8]` 是 `[3, 4, 5, 6, 7, 8]` 的一个子序列）_
 
-[subs="verbatim,quotes,macros"]
-----
-*Input:* [1,2,3,4,5,6,7,8]
-*Output:* 5
-*Explanation:
-*The longest subsequence that is fibonacci-like: [1,2,3,5,8].
-----
+*示例 1：*
 
-*Example 2:*
+....
+输入: arr = [1,2,3,4,5,6,7,8]
+输出: 5
+解释: 最长的斐波那契式子序列为 [1,2,3,5,8] 。
+....
 
-[subs="verbatim,quotes,macros"]
-----
-*Input:* [1,3,7,11,12,14,18]
-*Output:* 3
-*Explanation*:
-The longest subsequence that is fibonacci-like:
-[1,11,12], [3,11,14] or [7,11,18].
-----
+*示例 2：*
 
- 
+....
+输入: arr = [1,3,7,11,12,14,18]
+输出: 3
+解释: 最长的斐波那契式子序列有 [1,11,12]、[3,11,14] 以及 [7,11,18] 。
+....
 
-*Note:*
+*提示：*
 
+* `3 \<= arr.length \<= 1000`
+* `1 \<= arr[i] < arr[i + 1] \<= 10^9^`
 
-* `3 <= A.length <= 1000`
-* `1 <= A[0] < A[1] < ... < A[A.length - 1] <= 10^9`
-* _(The time limit has been reduced by 50% for submissions in Java, C, and C++.)_
 
+== 思路分析
 
+哈希！遍历数组，模拟斐波那契数列的计算过程。
 
+最优解是使用动态规划。回头尝试一下。
 
 [[src-0873]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0873_LengthOfLongestFibonacciSubsequence.java[tag=answer]
 ----
+--
+
+// 二刷::
+// +
+// --
+// [{java_src_attr}]
+// ----
+// include::{sourcedir}/_0873_LengthOfLongestFibonacciSubsequence_2.java[tag=answer]
+// ----
+// --
+====
+
+
+== 参考资料
 
+. https://leetcode.cn/problems/length-of-longest-fibonacci-subsequence/solutions/1656456/zui-chang-de-fei-bo-na-qi-zi-xu-lie-de-c-c4dt/[873. 最长的斐波那契子序列的长度 - 枚举+记忆化搜索+动态规划^]
+. https://leetcode.cn/problems/length-of-longest-fibonacci-subsequence/solutions/1654336/zui-chang-de-fei-bo-na-qi-zi-xu-lie-de-c-8trz/[873. 最长的斐波那契子序列的长度 - 官方题解^]
+. https://leetcode.cn/problems/length-of-longest-fibonacci-subsequence/solutions/1656437/by-ac_oier-beo2/[873. 最长的斐波那契子序列的长度 - 经典序列 DP 运用题^]

docs/index.adoc

@@ -1838,7 +1838,7 @@ include::0870-advantage-shuffle.adoc[leveloffset=+1]
 
 include::0872-leaf-similar-trees.adoc[leveloffset=+1]
 
-// include::0873-length-of-longest-fibonacci-subsequence.adoc[leveloffset=+1]
+include::0873-length-of-longest-fibonacci-subsequence.adoc[leveloffset=+1]
 
 // include::0874-walking-robot-simulation.adoc[leveloffset=+1]
 

logbook/202601.adoc

@@ -1186,6 +1186,10 @@ endif::[]
 |{doc_base_url}/0872-leaf-similar-trees.adoc[题解]
 |✅ 深度优先遍历。我用的是迭代法。
 
+|{counter:codes}
+|{leetcode_base_url}/length-of-longest-fibonacci-subsequence/[873. Length of Longest Fibonacci Subsequence^]
+|{doc_base_url}/0873-length-of-longest-fibonacci-subsequence.adoc[题解]
+|✅ 哈希。最优解是使用动态规划。遍历数组，模拟斐波那契数列的计算过程。
 
 
 |===

src/main/java/com/diguage/algo/leetcode/_0873_LengthOfLongestFibonacciSubsequence.java

@@ -0,0 +1,46 @@
+package com.diguage.algo.leetcode;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class _0873_LengthOfLongestFibonacciSubsequence {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2026-08-19 21:27:11
+   */
+  public int lenLongestFibSubseq(int[] arr) {
+    Set<Integer> set = new HashSet<>();
+    for (int num : arr) {
+      set.add(num);
+    }
+    int result = 0;
+    for (int i = 0; i < arr.length; i++) {
+      for (int j = i + 1; j < arr.length; j++) {
+        int a = arr[i];
+        int b = arr[j];
+        int len = 0;
+        if (arr[arr.length - 1] < (a + b)) {
+          break;
+        }
+        while (set.contains(a + b)) {
+          len++;
+          int temp = a + b;
+          System.out.println(a + " + " + b + " = " + temp);
+          a = b;
+          b = temp;
+        }
+        if (len > 0) {
+          result = Math.max(result, len + 2);
+        }
+      }
+    }
+    return result;
+  }
+
+  // end::answer[]
+  static void main() {
+    new _0873_LengthOfLongestFibonacciSubsequence()
+      .lenLongestFibSubseq(new int[]{2, 4, 7, 8, 9, 10, 14, 15, 18, 23, 32, 50});
+  }
+}