I was just doing virtual on 1338A - Powered Addition.

I wrote the following code: 121160133

and it out puts "63" on this test: N = 5, A = {-9, -2, -2, 7, 5} on both versions of C++17.

The probably problematic part is here:

int ans = 0, mx = -1e9;
for (int i = 0; i < N; i++) {
    mx = max(mx, A[i]);
    ans = max(ans, __lg(mx - A[i]) + 1);
    if(ans == 63){
        cout<<"ERROR\n";
        assert(false);
    }
}
cout << ans << '\n';

But I thought __lg(0) is -1? Also in custom invocation, the error message never appears.

Does anyone have any idea?