I was just wondering what will be the time complexity of O(10^8)
Your notation here implies that the time complexity does not depend on the size of the input. Hence, it can be said that your algorithm is constant time.
From my limited knowledge of competitive programming, if the time complexity is of O(10^8) it will run in 1 second. But this is risky. We cant give any assurity that it will run. But if it is 10^6, then it will definitely run within 0.1 seconds. Even O(10^7) is not risky. This will give you an idea before submitting the code whether it will lead to TLE or not looking at the worst case!!