A-star algorithm for Graph Matching [closed]

I am developing an application to mark block diagrams using neo4j together with graph matching. I am marking the diagrams by comparing the teacher's answer graph with the student's answer graph, and I am using graph matching for this. Currently I have implemented detecting of additions, deletions, and substitutions of nodes using Depth-first search in my own way, but I want to understand the other currently existing algorithms, and also know if they are better.

Many research papers have mentioned A-star algorithm for graph matching. I find it difficult to understand the pseudo codes in the research papers. I was mostly able to understand what they have described, which is not alot, but I want to understand completely. I would be grateful if someone could explain me how the A-star algorithm for graph matching works, or provide me a link with a better explanation about this algorithm used for error-tolerant graph matching using graph edit distance.

Some Research Paper Links:

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