What would be the value or code for an empty string array in C?

I am trying making a small program where users enter input and that input is stored into an array. I have an if statement (see below) that will end the loop obtaining input when nothing is entered. What would my if statement contain?

if (strings[j] == "") //When nothing is entered into the array, this path will be selected

What would I replace "" with? I have tried "NULL" but this doesn't appear to do anything. Anything helps, Thanks!