      "    * Queue the right child\n",
      "\n",
      "Complexity:\n",
      "* Time: O(n)\n",
      "* Space: O(n)"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
 
</s> remove     "    * Yes"
 </s> add     "    * Yes\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes\n",
    "* What should we do with each node when we process it?\n",
    "    * Call an input method `visit_func` on the node" </s> remove     "    * Yes"
 </s> add     "    * Yes\n",
    "* Can we assume this fits in memory?\n",
    "    * Yes\n",
    "* What should we do with each node when we process it?\n",
    "    * Call an input method `visit_func` on the node" </s> remove     "### Breadth-First Search\n",
 </s> add     "### Breadth-First Traversal\n", </s> remove     "### Breadth-First Search\n",
 </s> add     "### Breadth-First Traversal\n", </s> remove     "## Problem: Implement breadth-first search on a binary tree.\n",
 </s> add     "## Problem: Implement breadth-first traversal on a binary tree.\n",
    "* Space: O(n), extra space for the queue"
      "    * Queue the right child\n",
      "\n",
      "Complexity:\n",
      "* Time: O(n)\n",
    "* Space: O(n), extra space for the queue"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
keep keep keep keep replace keep keep keep keep keep
 Polish tree bfs challenge and solution (#77)

Update constraints and algorithm discussion. 
graphs_trees/tree_bfs/bfs_solution.ipynb