└── improvement


/improvement:
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  1 | #include <iostream>
  2 | #include <string>
  3 | #include <vector>
  4 | #include <ctime>
  5 | #include <sstream>
  6 | #include <iomanip>
  7 | #include <openssl/sha.h>
  8 | 
  9 | using namespace std;
 10 | 
 11 | class Block {
 12 | public:
 13 |     int index;
 14 |     string previousHash;
 15 |     string timestamp;
 16 |     string data; // Транзакції чи інші дані
 17 |     string hash;
 18 |     int nonce; // Параметр для майнінгу
 19 |     int difficulty;
 20 | 
 21 |     // Обчислення хешу блоку
 22 |     string calculateHash() const {
 23 |         stringstream ss;
 24 |         ss << index << previousHash << timestamp << data << nonce;
 25 |         return sha256(ss.str());
 26 |     }
 27 | 
 28 |     Block(int idx, string prevHash, string data, int difficulty)
 29 |         : index(idx), previousHash(prevHash), data(data), difficulty(difficulty) {
 30 |         timestamp = currentDateTime();
 31 |         nonce = 0; // початковий nonce
 32 |         hash = mineBlock();
 33 |     }
 34 | 
 35 |     // Функція для майнінгу блоку (Proof of Work)
 36 |     string mineBlock() {
 37 |         string target(difficulty, '0'); // Ціль для хешу, повинна починатись з певної кількості нулів
 38 |         while (hash.substr(0, difficulty) != target) {
 39 |             nonce++;
 40 |             hash = calculateHash();
 41 |         }
 42 |         return hash;
 43 |     }
 44 | 
 45 | private:
 46 |     // Обчислення хешу за допомогою SHA256
 47 |     string sha256(const string& str) const {
 48 |         unsigned char hash[SHA256_DIGEST_LENGTH];
 49 |         SHA256_CTX sha256_ctx;
 50 |         SHA256_Init(&sha256_ctx);
 51 |         SHA256_Update(&sha256_ctx, str.c_str(), str.length());
 52 |         SHA256_Final(hash, &sha256_ctx);
 53 | 
 54 |         stringstream ss;
 55 |         for (int i = 0; i < SHA256_DIGEST_LENGTH; i++) {
 56 |             ss << hex << setw(2) << setfill('0') << (int)hash[i];
 57 |         }
 58 |         return ss.str();
 59 |     }
 60 | 
 61 |     // Поточний час
 62 |     string currentDateTime() const {
 63 |         time_t now = time(0);
 64 |         struct tm tstruct;
 65 |         char buf[80];
 66 |         tstruct = *localtime(&now);
 67 |         strftime(buf, sizeof(buf), "%Y-%m-%d %X", &tstruct);
 68 |         return string(buf);
 69 |     }
 70 | };
 71 | 
 72 | class Blockchain {
 73 | private:
 74 |     vector<Block> chain;
 75 |     int difficulty;
 76 | 
 77 | public:
 78 |     Blockchain(int difficultyLevel) : difficulty(difficultyLevel) {
 79 |         // Створюємо перший блок (генезис)
 80 |         chain.push_back(Block(0, "0", "Genesis Block", difficulty));
 81 |     }
 82 | 
 83 |     void addBlock(const string& data) {
 84 |         Block newBlock(chain.back().index + 1, chain.back().hash, data, difficulty);
 85 | 
 86 |         if (isValidNewBlock(newBlock, chain.back())) {
 87 |             chain.push_back(newBlock);
 88 |             cout << "Block added: " << newBlock.hash << endl;
 89 |         } else {
 90 |             cout << "Failed to add block" << endl;
 91 |         }
 92 |     }
 93 | 
 94 |     bool isValidNewBlock(const Block& newBlock, const Block& prevBlock) {
 95 |         if (prevBlock.index + 1 != newBlock.index) {
 96 |             cout << "Invalid index" << endl;
 97 |             return false;
 98 |         }
 99 |         if (prevBlock.hash != newBlock.previousHash) {
100 |             cout << "Invalid previous hash" << endl;
101 |             return false;
102 |         }
103 |         if (newBlock.hash != newBlock.calculateHash()) {
104 |             cout << "Invalid hash" << endl;
105 |             return false;
106 |         }
107 |         return true;
108 |     }
109 | 
110 |     bool isChainValid() {
111 |         for (int i = 1; i < chain.size(); i++) {
112 |             if (!isValidNewBlock(chain[i], chain[i - 1])) {
113 |                 return false;
114 |             }
115 |         }
116 |         return true;
117 |     }
118 | 
119 |     void printBlockchain() {
120 |         for (const Block& block : chain) {
121 |             cout << "Block " << block.index << " [Hash: " << block.hash << "]" << endl;
122 |             cout << "Timestamp: " << block.timestamp << endl;
123 |             cout << "Data: " << block.data << endl;
124 |             cout << "Previous Hash: " << block.previousHash << endl;
125 |             cout << "Nonce: " << block.nonce << endl;
126 |             cout << "Difficulty: " << block.difficulty << endl;
127 |             cout << "---------------------------------" << endl;
128 |         }
129 |     }
130 | 
131 |     bool validateBlockchain() {
132 |         return isChainValid();
133 |     }
134 | 
135 |     const vector<Block>& getChain() const {
136 |         return chain;
137 |     }
138 | };
139 | 
140 | int main() {
141 |     Blockchain myBlockchain(4);  // Створюємо блокчейн з рівнем складності 4 (хеш починається з 4 нулів)
142 | 
143 |     myBlockchain.addBlock("First Block after Genesis");
144 |     myBlockchain.addBlock("Second Block with transactions");
145 | 
146 |     myBlockchain.printBlockchain();
147 | 
148 |     if (myBlockchain.validateBlockchain()) {
149 |         cout << "Blockchain is valid!" << endl;
150 |     } else {
151 |         cout << "Blockchain is invalid!" << endl;
152 |     }
153 | 
154 |     return 0;
155 | }
156 | 


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