## README ¶

### 873. Length of Longest Fibonacci Subsequence (Medium)

A sequence `X`

is _{1}, X_{2}, ..., X_{n}*Fibonacci-like* if:

`n >= 3`

`X`

for all_{i}+ X_{i+1}= X_{i+2}`i + 2 <= n`

Given a **strictly increasing** array `arr`

of positive integers forming a sequence, return the **length** of the longest Fibonacci-like subsequence of `arr`

. If one does not exist, return `0`

.

*A subsequence is derived from another sequence arr by deleting any number of elements (including none) from arr, without changing the order of the remaining elements. For example, [3, 5, 8] is a subsequence of [3, 4, 5, 6, 7, 8].*

**Example 1:**

Input:arr = [1,2,3,4,5,6,7,8]Output:5Explanation:The longest subsequence that is fibonacci-like: [1,2,3,5,8].

**Example 2:**

Input:arr = [1,3,7,11,12,14,18]Output:3Explanation:The longest subsequence that is fibonacci-like: [1,11,12], [3,11,14] or [7,11,18].

**Constraints:**

`3 <= arr.length <= 1000`

`1 <= arr[i] < arr[i + 1] <= 10`

^{9}

#### Related Topics

#### Similar Questions

- Fibonacci Number (Easy)

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