Problem
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.
Constraints
0 ≤ people ≤ 1,000,000,000. The answer fits a signed 64-bit integer.
Examples
Example 1
Input:
people = 4
Expected output:
expected = 6Input:
long long people = 4;
Expected output:
long long expected = 6;Input:
long people = 4;
Expected output:
long expected = 6;Explanation
The pairs are AB, AC, AD, BC, BD, and CD: six handshakes.
Example 2
Input:
people = 1
Expected output:
expected = 0Input:
long long people = 1;
Expected output:
long long expected = 0;Input:
long people = 1;
Expected output:
long expected = 0;Explanation
One person has nobody else to greet.
References
This challenge is adapted for CodeUtility. Follow the statement and constraints above.