Problème
Begin the sequence with 1 and 2. Each following term is the sum of the previous two. Include only even-valued terms no greater than limit, then add them.
Implement even_fibonacci_sum(limit).
Input
limit: The largest term value that may be included.
Output
Return the sum, or 0 if there are no eligible terms.
Contraintes
0 ≤ limit ≤ 10¹⁵. The result fits a signed 64-bit integer.
Exemples
Entrée :
limit = 50
Sortie attendue :
expected = 44Entrée :
long long limit = 50;
Sortie attendue :
long long expected = 44;Entrée :
long limit = 50;
Sortie attendue :
long expected = 44;Explication
The even terms are 2, 8, and 34. Their sum is 44.
Entrée :
limit = 1
Sortie attendue :
expected = 0Entrée :
long long limit = 1;
Sortie attendue :
long long expected = 0;Entrée :
long limit = 1;
Sortie attendue :
long expected = 0;Explication
The first even term is 2, which exceeds the limit.
Comment l'aborder
Essayez d'abord seul, puis ouvrez les indices un par un.
Indice 1
You only need the even Fibonacci terms, not the entire sequence.
Indice 2
Generate the sequence until the next term exceeds the limit and add qualifying terms.
Indice 3
Watch the boundary when the limit itself is a Fibonacci term.
Complexité attendue
O(log limit) time, O(1) extra space
Références
Ce défi a été adapté pour CodeUtility. Suivez l'énoncé et les contraintes ci-dessus.