[Swift]LeetCode873. 最长的斐波那契子序列的长度 | 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 th