A transaction has in-bitcoin address. Transaction tells to transfer that address (in fraction or whole) to another address. Since the source of truth is block-chain, how does miner know that in-bitcoin address has said amount of data ? And how does miner check it efficiently ?
I have read about Merkel trees. My understanding is that they help to find whether a transaction is present in specific order in a block. But a block chain will have many blocks. So, how is it done efficiently by miners ?
Will not creating a hashmap from bitcoin-address to amount will be easier ?