在区块中加入Merkle Root字段

def solve(block, transactions):
    import hashlib
    import copy
    import json
    b = copy.deepcopy(block)
    if transactions:
        while len(transactions) > 1:
            if len(transactions) % 2 == 1:
                transactions.append(transactions[-1])
            transactions = [hashlib.sha256((transactions[i] + transactions[i+1]).encode()).hexdigest() for i in range(0, len(transactions), 2)]
        b['merkle_root'] = transactions[0] if transactions else ''
    print(b)