i need to implement following functions:
BlockChain BlockChainLoad(std::ifstream& file)
void BlockChainAppendTransaction( BlockChain& blockChain, const Transaction& transaction, const string& timestamp

i can adjust the struct of blockchain as i wish, so each new block will be connected to the previous once(and contain transaction ,time ).

i tried 2 ways :
1)blockchain struct will have 2 pointers , next and previous.
2)creat new struct that will contain only a pointer to head of some blockchain.

with both ways i still cannot implement the requseted function as needed.

what is the best approach to such problem?
i cannot change ethe functions declaration .