     "metadata": {},
     "source": [
      "## Constraints\n",
      "\n",
      "* Can we assume we are working with valid integers?\n",
      "    * Yes\n",
      "* Can we assume all left descendents <= n < all right descendents?\n",
      "    * Yes\n",
 
</s> remove     "    * This is optional"
 </s> add     "    * This is optional\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes" </s> remove     "    * This is optional"
 </s> add     "    * This is optional\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes"
    "* Can we insert None values?\n",
    "    * No\n",
     "metadata": {},
     "source": [
      "## Constraints\n",
      "\n",
    "* Can we insert None values?\n",
    "    * No\n",
      "* Can we assume we are working with valid integers?\n",
      "    * Yes\n",
      "* Can we assume all left descendents <= n < all right descendents?\n",
      "    * Yes\n",
keep keep keep add keep keep keep keep
 Polish bst challenge and solution (#75)

Update constraints, algorithm discussion, and code. 
graphs_trees/bst/bst_solution.ipynb