COVID Handshake Problem
E · easyP · Verified PYQmath
Problem
Before the outbreak of coronavirus, a meeting took place in Wuhan. A person who attended had COVID-19 and everyone shook hands with everyone else exactly once. Given N people in the room, find the total number of handshakes. Input: First line = T (test cases). Each following line = N (number of people).
Constraints
1<=T<=1000, 0<N<10\*\*6
Example
Input
2 1 2
Output
0 1
Total handshakes = N\*(N-1)/2. Use long long to avoid overflow for large N.
1 person → 0 handshakes. 2 people → 1 handshake. Formula: N\*(N-1)/2