Divisible by 60

• Time : $O(n)$
• Space : $O(1)$

int Solution::divisibleBy60(vector<int> &A) {
    if(A.size() == 1) return A[0] == 0;
    if(A.size() == 2) return (A[0] == 0 and A[1] == 6) or (A[0] == 6 and A[1] == 0);
    int sum = 0, zero = 0;
    for(auto a : A) {
        if(a == 0) zero = 1;
        sum += a;
    }
    return sum % 3 == 0 and zero;
}