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Polish bst challenge and solution (#75)

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Update constraints, algorithm discussion, and code.
This commit is contained in:
Donne Martin 2016-06-24 07:23:20 -04:00 committed by GitHub
parent c7e9a85db7
commit c24a628329
3 changed files with 30 additions and 20 deletions
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11
graphs_trees/bst/bst.py
View File

@ -11,20 +11,19 @@ class Node(object):
def insert(root, data): def insert(root, data):
# Constraint: Assume we are working with valid ints
if root is None: if root is None:
root = Node(data) root = Node(data)
return root return root
if data <= root.data: if data <= root.data:
if root.left is None: if root.left is None:
root.left = Node(data) root.left = insert(root.left, data)
root.left.parent = root root.left.parent = root
return root.left
else: else:
return insert(root.left, data) insert(root.left, data)
else: else:
if root.right is None: if root.right is None:
root.right = Node(data) root.right = insert(root.right, data)
root.right.parent = root root.right.parent = root
return root.right
else: else:
return insert(root.right, data) insert(root.right, data)

14
graphs_trees/bst/bst_challenge.ipynb
View File

@ -33,6 +33,8 @@
"source": [ "source": [
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"* Can we insert None values?\n",
" * No\n",
"* Can we assume we are working with valid integers?\n", "* Can we assume we are working with valid integers?\n",
" * Yes\n", " * Yes\n",
"* Can we assume all left descendents <= n < all right descendents?\n", "* Can we assume all left descendents <= n < all right descendents?\n",
@ -40,7 +42,9 @@
"* For simplicity, can we use just a Node class without a wrapper Tree class?\n", "* For simplicity, can we use just a Node class without a wrapper Tree class?\n",
" * Yes\n", " * Yes\n",
"* Do we have to keep track of the parent nodes?\n", "* Do we have to keep track of the parent nodes?\n",
" * This is optional" " * This is optional\n",
"* Can we assume this fits in memory?\n",
" * Yes"
] ]
}, },
{ {
@ -53,12 +57,14 @@
"\n", "\n",
"Insert will be tested through the following traversal:\n", "Insert will be tested through the following traversal:\n",
"\n", "\n",
"### In-Order Traversal (Provided)\n", "### In-Order Traversal\n",
"\n", "\n",
"* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n", "* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n",
"* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n", "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
"\n", "\n",
"If the `root` input is `None`, return a tree with the only element being the new root node." "If the `root` input is `None`, return a tree with the only element being the new root node.\n",
"\n",
"You do not have to code the in-order traversal, it is part of the unit test."
] ]
}, },
{ {
@ -206,7 +212,7 @@
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython3", "pygments_lexer": "ipython3",
"version": "3.4.3" "version": "3.5.0"
} }
}, },
"nbformat": 4, "nbformat": 4,

25
graphs_trees/bst/bst_solution.ipynb
View File

@ -33,6 +33,8 @@
"source": [ "source": [
"## Constraints\n", "## Constraints\n",
"\n", "\n",
"* Can we insert None values?\n",
" * No\n",
"* Can we assume we are working with valid integers?\n", "* Can we assume we are working with valid integers?\n",
" * Yes\n", " * Yes\n",
"* Can we assume all left descendents <= n < all right descendents?\n", "* Can we assume all left descendents <= n < all right descendents?\n",
@ -40,7 +42,9 @@
"* For simplicity, can we use just a Node class without a wrapper Tree class?\n", "* For simplicity, can we use just a Node class without a wrapper Tree class?\n",
" * Yes\n", " * Yes\n",
"* Do we have to keep track of the parent nodes?\n", "* Do we have to keep track of the parent nodes?\n",
" * This is optional" " * This is optional\n",
"* Can we assume this fits in memory?\n",
" * Yes"
] ]
}, },
{ {
@ -53,12 +57,14 @@
"\n", "\n",
"Insert will be tested through the following traversal:\n", "Insert will be tested through the following traversal:\n",
"\n", "\n",
"### In-Order Traversal (Provided)\n", "### In-Order Traversal\n",
"\n", "\n",
"* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n", "* 5, 2, 8, 1, 3 -> 1, 2, 3, 5, 8\n",
"* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n", "* 1, 2, 3, 4, 5 -> 1, 2, 3, 4, 5\n",
"\n", "\n",
"If the `root` input is `None`, return a tree with the only element being the new root node." "If the `root` input is `None`, return a tree with the only element being the new root node.\n",
"\n",
"You do not have to code the in-order traversal, it is part of the unit test."
] ]
}, },
{ {
@ -122,23 +128,22 @@
"\n", "\n",
"\n", "\n",
"def insert(root, data):\n", "def insert(root, data):\n",
" # Constraint: Assume we are working with valid ints\n",
" if root is None:\n", " if root is None:\n",
" root = Node(data)\n", " root = Node(data)\n",
" return root\n", " return root\n",
" if data <= root.data:\n", " if data <= root.data:\n",
" if root.left is None:\n", " if root.left is None:\n",
" root.left = Node(data)\n", " root.left = insert(root.left, data)\n",
" root.left.parent = root\n", " root.left.parent = root\n",
" return root.left\n",
" else:\n", " else:\n",
" return insert(root.left, data)\n", " insert(root.left, data)\n",
" else:\n", " else:\n",
" if root.right is None:\n", " if root.right is None:\n",
" root.right = Node(data)\n", " root.right = insert(root.right, data)\n",
" root.right.parent = root\n", " root.right.parent = root\n",
" return root.right\n",
" else:\n", " else:\n",
" return insert(root.right, data)" " insert(root.right, data)"
] ]
}, },
{ {
@ -272,7 +277,7 @@
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython3", "pygments_lexer": "ipython3",
"version": "3.4.3" "version": "3.5.0"
} }
}, },
"nbformat": 4, "nbformat": 4,