Is Three Fibonacci Sum easy or hard?

It is an easy problem with a 62.1 percent acceptance rate on FleetCode. The main challenge is realizing that the Fibonacci list is tiny, which makes a quadratic search fast. Once you see that, the implementation is only a few lines.

How to solve Three Fibonacci Sum in O(n)?

Because the Fibonacci list has only about log n elements, you cannot reduce the search below O(F^2) by treating it as a general array problem. To get close to linear behavior, reduce the search to one pass: for each candidate first term, check whether the remainder is a sum of two Fibonacci numbers using a precomputed set. Practically, the search stays near-linear in the target's bit length.

Three Fibonacci Sum Python and Java solution?

In Python, generate Fibonacci numbers with a while loop into a list, convert it to a set, and nest one loop over the list with a set lookup for the third term. In Java, build an ArrayList of longs, store values in a HashSet , and use the same nested loop with contains(). Use long types in Java because Fibonacci values can overflow int quickly.

What is the best approach for Three Fibonacci Sum?

The best approach is to precompute all Fibonacci numbers up to the target, then fix the first term and use a hash set to look up the remaining needed value. This runs in O(F^2) time, where F is the count of Fibonacci numbers below the target, which is roughly log of the target. Two pointers on the sorted list give the same complexity with O(F) space.

What data structure is used in Three Fibonacci Sum?

The solution uses an array or list to store the Fibonacci numbers in increasing order, and a hash set for constant-time membership checks. The two-pointer variant replaces the hash set with index pointers on the sorted array. Both structures take O(F) space.

What is the time complexity of Three Fibonacci Sum?

The optimal solution runs in O(F^2) time, where F is the number of Fibonacci values up to the target, about 40 for targets near 10^9. The brute force triple loop runs in O(F^3). Generating the Fibonacci list itself takes O(F) time and space.

Is Three Fibonacci Sum asked at Google, Amazon, or Meta?

This problem is tagged General on FleetCode and does not have confirmed company tags in the dataset. It tests basic number generation, hashing, and search pruning, which appear in many interview rounds. Treat it as a warm-up problem rather than a company-specific question.

4078. Three Fibonacci Sum - Practice Online

You are given an integer n.

The Fibonacci sequence starts with 0 and 1, and each subsequent number is the sum of the previous two numbers. Its first few terms are 0, 1, 1, 2, 3, 5, 8, 13, ....

Return true if n can be expressed as the sum of three consecutive terms in the Fibonacci sequence, and false otherwise.

Example 1:

Input: n = 16

Output: true

Explanation:

The three consecutive terms 3, 5, and 8 have a sum of 3 + 5 + 8 = 16.

Example 2:

Input: n = 8

Output: false

Explanation:

Although 1 + 2 + 5 = 8, these terms are not consecutive in the Fibonacci sequence. No three consecutive terms have a sum of 8.

Example 3:

Input: n = 2

Output: true

Explanation:

The first three terms have a sum of 0 + 1 + 1 = 2.

Constraints:

1 <= n <= 10⁹