title: Array/List that can Grow in two directions?
body: <p>Ok so here is my Goal:</p>
  <ul>
  <li>An Array that I can expand at the end end the beginning without messing up the indices</li>
  <li>A object that was input at index 3 should remain at index 3 even if I want to add a new object
  at position '-1' (-1 being the position before the initial start position)</li>
  <li>There can be empty Cells in the Array which could be filled later</li>
  </ul>
  <p>What I thought of so far:</p>
  <ul>
  <li>Using Dictionaries with strings
  <ul>
  <li>probably to inefficient parsing between string and number all the time</li>
  </ul>
  </li>
  <li>Using an Offset and just making the Array Bigger
  <ul>
  <li>I think this would result in creating a lot of arrays which sounds very inefficient
  <ul>
  <li>Maybe some smarter algorithm to increase array size would work (doubling it/increasing it by 25 instead of 1)</li>
  </ul>
  </li>
  </ul>
  </li>
  <li>Using two Arrays one for positive values one for negative ones
  <ul>
  <li>Seems pretty hard to work with when near position Zero</li>
  </ul>
  </li>
  </ul>
  <p>What do I need this for:<br />
  I want to make a game where the 2D grid based world can be expanded by the player and things like the tiles around a new placed tile are very important (kind of  a mix between dorfromantik and Islanders)</p>