Problème
Afficher la traductionThe factorial of n, written n!, is 1 × 2 × … × n. By definition 0! = 1.
Implement factorial(n).
Input
n: A non-negative integer.
Output
Return n!.
Contraintes
0 ≤ n ≤ 20, so the result fits a signed 64-bit integer.
Exemples
Exemple 1
Entrée :
n = 5
Sortie attendue :
expected = 120Entrée :
long long n = 5;
Sortie attendue :
long long expected = 120;Entrée :
long n = 5;
Sortie attendue :
long expected = 120;Explication
1 × 2 × 3 × 4 × 5 = 120.
Exemple 2
Entrée :
n = 0
Sortie attendue :
expected = 1Entrée :
long long n = 0;
Sortie attendue :
long long expected = 1;Entrée :
long n = 0;
Sortie attendue :
long expected = 1;Explication
0! is defined as 1.