Can anyone explain to me about A* algorithm?
> Can anyone explain to me about A* algorithm?
Again, use a search engine to find some tutorials and start reading.
We're not here to read for you and spoon-feed it to you here one sentence at a time.
If you have specific questions later on, then we can deal with that, say
"I don't understand what paragraph 4.2 on <some website> is trying to do".
That would show us that you've made the effort.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.