There is no automatic system that can tell you whether your idea has been done or the similarity between your idea and the most similar previous work.
Search all possible keywords (e.g., synonym) in Google/Google Scholar.
If there exist old and recent surveys, carefully read them. Otherwise, make a survey on your own.
Quickly go through previous works to ensure that your idea has not been done. You do not need to understand the details of their methods. Actually, telling whether their methods are close to yours is much simpler. For instance, you can just pay attention to the most obvious parts (e.g., flowchart, objective function, and abstract) in their papers.
Through the above steps, identify the most related work, think about the difference and your advantage. If you cannot clearly state the difference and advantage of your idea, do not work on it.