The question ask you to build an IP store. Support

adding IP (prefix)
searching for IP
counting how many IPs.
But I am so confused about the second part, they said you can only add IP as a prefix. They give me an example of binary string.
Imagine adding 1111/4 bits and adding 11/2bits into your data store, the counting should be 4, as 11 encapsulates all possibility of 11(00,01,10,11).
I manage to implement the add and search pretty quickly, and implement a dfs do counting each time using exponential (alphabet size) * length stuff, which is inefficient. I think I will get rejected possibly.The interviewer seems unhappy and uninterested.

I was so disappointed with myself. I was so tired and burn out. I feel hopeless and stuck in a endless loop of anxiety just for securing a job. I really want to quit.
Sorry for the negativity.