Problème
Every person shakes hands once with every other person. A handshake between A and B is the same event as one between B and A. Nobody shakes their own hand.
Implement handshake_count(people).
Input
people: The number of people.
Output
Return the total number of distinct handshakes.
Contraintes
0 ≤ people ≤ 1,000,000,000. The answer fits a signed 64-bit integer.
Exemples
Entrée :
people = 4
Sortie attendue :
expected = 6Entrée :
long long people = 4;
Sortie attendue :
long long expected = 6;Entrée :
long people = 4;
Sortie attendue :
long expected = 6;Explication
The pairs are AB, AC, AD, BC, BD, and CD: six handshakes.
Entrée :
people = 1
Sortie attendue :
expected = 0Entrée :
long long people = 1;
Sortie attendue :
long long expected = 0;Entrée :
long people = 1;
Sortie attendue :
long expected = 0;Explication
One person has nobody else to greet.
Comment l'aborder
Essayez d'abord seul, puis ouvrez les indices un par un.
Indice 1
Each handshake is just an unordered pair of distinct people.
Indice 2
Count how many pairs can be formed from all people without double-counting.
Indice 3
Be careful that zero or one person means no handshakes at all.
Complexité attendue
O(1) time, O(1) extra space
Références
Ce défi a été adapté pour CodeUtility. Suivez l'énoncé et les contraintes ci-dessus.