Minimum Operations to Make Array Equal — C++

// Time:  O(1)
// Space: O(1)

class Solution {
public:
    int minOperations(int n) {
        // total = sum(2i+1 for i in xrange(n)) = n^2
        // left_half_total = sum(2i+1 for i in xrange(n//2)) = (n//2)^2
        // result = (n//2) * (total//n) - left_half_total = (n//2)*(n-n//2) = (n//2)*((n+1)//2)
        return (n / 2) * ((n + 1) / 2);
    }
};