title: Fastest Way to Merge Multilevel HashMaps
body: <p>I have many Multilevel HashMaps in which deepest element is List. Number of Levels may vary. </p>
  
  <p>Intuitively lets say first hashmap is </p>
  
  <pre><code>{
      "com": {
          "avalant": {
              "api": []
          }
      }
  }
  </code></pre>
  
  <p>and second hashmap is </p>
  
  <pre><code>{
      "com": {
          "google": {
              "service": {
                  "api": []
              }
          }
      }
  }   
  </code></pre>
  
  <p>After merge it should become</p>
  
  <pre><code>{
      "com": {
          "avalant": {
              "api": []
          },
          "google": {
              "service": {
                  "api": []
              }
          }
      }
  }
  </code></pre>
  
  <p>What is the best way to merge them ? Just iterate two maps at a time and combine would be good idea ? </p>