A sequence X_1, X_2, ..., X_n
is fibonacci-like if:
n >= 3
-
X_i + X_{i+1} = X_{i+2}
for alli + 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]
.)
Example 1:
Input: [1,2,3,4,5,6,7,8]
Output: 5
Explanation: The longest subsequence that is fibonacci-like: [1,2,3,5,8].
Example 2:
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].
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++.)
参考资料:
https://leetcode.com/problems/length-of-longest-fibonacci-subsequence/