This is a problem from Leetcode - Length of Longest Fibonacci Subsequence.

A sequence X_1, X_2, …, X_n is fibonacci-like if:

- 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.

Example :

1 | Input: [1,2,3,4,5,6,7,8] |

Note:

- 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++.)