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  1. #include <iostream>
  2. #include <map>
  3. #include <string>
  4. #include <functional>
  5.  
  6. using namespace std;
  7.  
  8. class ConsistentHashing {
  9. private:
  10.     // hash position -> server name
  11.     map<size_t, string> ring;
  12.  
  13.     size_t getHash(const string& value) {
  14.         return hash<string>{}(value);
  15.     }
  16.  
  17. public:
  18.     void addServer(const string& server) {
  19.         size_t hashValue = getHash(server);
  20.  
  21.         ring[hashValue] = server;
  22.  
  23.         cout << "Added " << server
  24.              << " at position " << hashValue << "\n";
  25.     }
  26.  
  27.     void removeServer(const string& server) {
  28.         size_t hashValue = getHash(server);
  29.  
  30.         ring.erase(hashValue);
  31.  
  32.         cout << "Removed " << server << "\n";
  33.     }
  34.  
  35.     string getServer(const string& key) {
  36.         if (ring.empty())
  37.             return "No servers available";
  38.  
  39.         size_t keyHash = getHash(key);
  40.  
  41.         // Find the first server clockwise
  42.         auto it = ring.lower_bound(keyHash);
  43.  
  44.         // If we reached the end of the ring,
  45.         // wrap around to the first server
  46.         if (it == ring.end()) {
  47.             it = ring.begin();
  48.         }
  49.  
  50.         return it->second;
  51.     }
  52.  
  53.     void printRing() {
  54.         cout << "\n--- Hash Ring ---\n";
  55.  
  56.         for (auto& [hashValue, server] : ring) {
  57.             cout << hashValue
  58.                  << " -> "
  59.                  << server << "\n";
  60.         }
  61.     }
  62. };
  63.  
  64. int main() {
  65.  
  66.     ConsistentHashing ch;
  67.  
  68.     // Add servers
  69.     ch.addServer("Server-A");
  70.     ch.addServer("Server-B");
  71.     ch.addServer("Server-C");
  72.  
  73.     ch.printRing();
  74.  
  75.     cout << "\n--- Key Mapping ---\n";
  76.  
  77.     string keys[] = {
  78.         "user_101",
  79.         "user_102",
  80.         "user_103",
  81.         "user_104",
  82.         "user_105"
  83.     };
  84.  
  85.     for (const string& key : keys) {
  86.         cout << key
  87.              << " -> "
  88.              << ch.getServer(key)
  89.              << "\n";
  90.     }
  91.  
  92.     // Add a new server
  93.     cout << "\nAdding Server-D...\n\n";
  94.  
  95.     ch.addServer("Server-D");
  96.  
  97.     cout << "--- Key Mapping After Adding Server-D ---\n";
  98.  
  99.     for (const string& key : keys) {
  100.         cout << key
  101.              << " -> "
  102.              << ch.getServer(key)
  103.              << "\n";
  104.     }
  105.  
  106.     return 0;
  107. }
Success #stdin #stdout 0s 5320KB
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stdin
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Standard input is empty
stdout
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Added Server-A at position 1934068100283367141
Added Server-B at position 8475661567887905832
Added Server-C at position 8522928446594188189

--- Hash Ring ---
1934068100283367141 -> Server-A
8475661567887905832 -> Server-B
8522928446594188189 -> Server-C

--- Key Mapping ---
user_101 -> Server-A
user_102 -> Server-A
user_103 -> Server-A
user_104 -> Server-A
user_105 -> Server-A

Adding Server-D...

Added Server-D at position 15032801287774326687
--- Key Mapping After Adding Server-D ---
user_101 -> Server-D
user_102 -> Server-A
user_103 -> Server-A
user_104 -> Server-A
user_105 -> Server-A
https://ideone.com/jh5Veg
language:
C++ (gcc 8.3)
created:
5 days ago
visibility:
public

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