Where Would It Go?

nums is sorted from smallest to largest, and target is a number. Return where target belongs in nums:

• If target is in nums, return its index.
• If not, return the index it would take if you slotted it in without breaking the sorted order.

Rules:

• The values in nums are all different.
• If nums is empty, return 0.
• If target is bigger than everything in nums, return nums.length.
• nums can hold up to 1,000,000 numbers and the function runs many times. So it must take O(log n) time.