Problema
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.
Restrições
0 ≤ people ≤ 1,000,000,000. The answer fits a signed 64-bit integer.
Exemplos
Entrada:
people = 4
Saída esperada:
expected = 6Entrada:
long long people = 4;
Saída esperada:
long long expected = 6;Entrada:
long people = 4;
Saída esperada:
long expected = 6;Explicação
The pairs are AB, AC, AD, BC, BD, and CD: six handshakes.
Entrada:
people = 1
Saída esperada:
expected = 0Entrada:
long long people = 1;
Saída esperada:
long long expected = 0;Entrada:
long people = 1;
Saída esperada:
long expected = 0;Explicação
One person has nobody else to greet.
Como abordar
Tente sozinho primeiro e depois abra uma dica de cada vez.
Dica 1
Each handshake is just an unordered pair of distinct people.
Dica 2
Count how many pairs can be formed from all people without double-counting.
Dica 3
Be careful that zero or one person means no handshakes at all.
Complexidade esperada
O(1) time, O(1) extra space
Referências
Este desafio foi adaptado para o CodeUtility. Siga o enunciado e as restrições acima.