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Polish stack solution.

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This commit is contained in:
Donne Martin
2016-02-20 08:11:49 -05:00
parent 08fabdf58d
commit 7a166bed67
2 changed files with 23 additions and 29 deletions
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21
stacks_queues/stack/stack.py
View File

@@ -1,8 +1,8 @@
class Node(object): class Node(object):
def __init__(self, data): def __init__(self, data, next=None):
self.data = data self.data = data
self.next = None self.next = next
class Stack(object): class Stack(object):
@@ -11,21 +11,18 @@ class Stack(object):
self.top = top self.top = top
def push(self, data): def push(self, data):
node = Node(data) node = Node(data, self.top)
node.next = self.top
self.top = node self.top = node
def pop(self): def pop(self):
if self.top is not None: if self.top is None:
data = self.top.data return None
self.top = self.top.next data = self.top.data
return data self.top = self.top.next
return None return data
def peek(self): def peek(self):
if self.top is not None: return self.top.data if self.top is not None else None
return self.top.data
return None
def is_empty(self): def is_empty(self):
return self.peek() is None return self.peek() is None

31
stacks_queues/stack/stack_solution.ipynb
View File

@@ -137,9 +137,9 @@
"%%writefile stack.py\n", "%%writefile stack.py\n",
"class Node(object):\n", "class Node(object):\n",
"\n", "\n",
" def __init__(self, data):\n", " def __init__(self, data, next=None):\n",
" self.data = data\n", " self.data = data\n",
" self.next = None\n", " self.next = next\n",
"\n", "\n",
"\n", "\n",
"class Stack(object):\n", "class Stack(object):\n",
@@ -148,21 +148,18 @@
" self.top = top\n", " self.top = top\n",
"\n", "\n",
" def push(self, data):\n", " def push(self, data):\n",
" node = Node(data)\n", " node = Node(data, self.top)\n",
" node.next = self.top\n",
" self.top = node\n", " self.top = node\n",
"\n", "\n",
" def pop(self):\n", " def pop(self):\n",
" if self.top is not None:\n", " if self.top is None:\n",
" data = self.top.data\n", " return None\n",
" self.top = self.top.next\n", " data = self.top.data\n",
" return data\n", " self.top = self.top.next\n",
" return None\n", " return data\n",
"\n", "\n",
" def peek(self):\n", " def peek(self):\n",
" if self.top is not None:\n", " return self.top.data if self.top is not None else None\n",
" return self.top.data\n",
" return None\n",
"\n", "\n",
" def is_empty(self):\n", " def is_empty(self):\n",
" return self.peek() is None" " return self.peek() is None"
@@ -308,21 +305,21 @@
], ],
"metadata": { "metadata": {
"kernelspec": { "kernelspec": {
"display_name": "Python 2", "display_name": "Python 3",
"language": "python", "language": "python",
"name": "python2" "name": "python3"
}, },
"language_info": { "language_info": {
"codemirror_mode": { "codemirror_mode": {
"name": "ipython", "name": "ipython",
"version": 2 "version": 3
}, },
"file_extension": ".py", "file_extension": ".py",
"mimetype": "text/x-python", "mimetype": "text/x-python",
"name": "python", "name": "python",
"nbconvert_exporter": "python", "nbconvert_exporter": "python",
"pygments_lexer": "ipython2", "pygments_lexer": "ipython3",
"version": "2.7.10" "version": "3.4.3"
} }
}, },
"nbformat": 4, "nbformat": 4,