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Polish set of stacks solution

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Donne Martin
2016-02-21 16:21:37 -05:00
parent 7222f71f59
commit d9b2d7144e
2 changed files with 23 additions and 31 deletions
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49
stacks_queues/set_of_stacks/set_of_stacks_solution.ipynb
View File

@@ -35,7 +35,7 @@
"\n", "\n",
"* Can we assume we already have a stack class that can be used for this problem?\n", "* Can we assume we already have a stack class that can be used for this problem?\n",
" * Yes\n", " * Yes\n",
"* If a stack becomes full, we should automatically create one?\n", "* If a stack becomes full, should we automatically create one?\n",
" * Yes\n", " * Yes\n",
"* If a stack becomes empty, should we delete it?\n", "* If a stack becomes empty, should we delete it?\n",
" * Yes" " * Yes"
@@ -50,7 +50,7 @@
"* Push and pop on an empty stack\n", "* Push and pop on an empty stack\n",
"* Push and pop on a non-empty stack\n", "* Push and pop on a non-empty stack\n",
"* Push on a capacity stack to create a new one\n", "* Push on a capacity stack to create a new one\n",
"* Pop on a one element stack to destroy it" "* Pop on a stack to destroy it"
] ]
}, },
{ {
@@ -67,7 +67,7 @@
"\n", "\n",
"Complexity:\n", "Complexity:\n",
"* Time: O(1)\n", "* Time: O(1)\n",
"* Space: O(1)\n", "* Space: O(m), where m is the size of the new stack\n",
"\n", "\n",
"### Pop\n", "### Pop\n",
"\n", "\n",
@@ -113,21 +113,19 @@
"class StackWithCapacity(Stack):\n", "class StackWithCapacity(Stack):\n",
"\n", "\n",
" def __init__(self, top=None, capacity=10):\n", " def __init__(self, top=None, capacity=10):\n",
" super(StackWithCapacity, self).__init__(top)\n",
" self.capacity = capacity\n", " self.capacity = capacity\n",
" self.num_items = 0\n", " self.num_items = 0\n",
" super(StackWithCapacity, self).__init__(top)\n",
"\n", "\n",
" def push(self, data):\n", " def push(self, data):\n",
" if self.num_items < self.capacity:\n", " if self.is_full():\n",
" super(StackWithCapacity, self).push(data)\n",
" self.num_items += 1\n",
" else:\n",
" raise Exception('Stack full')\n", " raise Exception('Stack full')\n",
" super(StackWithCapacity, self).push(data)\n",
" self.num_items += 1\n",
"\n", "\n",
" def pop(self):\n", " def pop(self):\n",
" data = super(StackWithCapacity, self).pop()\n",
" self.num_items -= 1\n", " self.num_items -= 1\n",
" return data\n", " return super(StackWithCapacity, self).pop()\n",
"\n", "\n",
" def is_full(self):\n", " def is_full(self):\n",
" return self.num_items == self.capacity\n", " return self.num_items == self.capacity\n",
@@ -148,17 +146,13 @@
"\n", "\n",
" def pop(self):\n", " def pop(self):\n",
" if self.last_stack is None:\n", " if self.last_stack is None:\n",
" return\n", " return None\n",
" elif self.last_stack.top.next is None:\n", " data = self.last_stack.pop()\n",
" data = self.last_stack.pop()\n", " if self.last_stack.num_items == 0:\n",
" self.stacks.pop()\n", " self.stacks.pop()\n",
" self.last_stack = self.stacks[len(self.stacks)-1] \\\n",
" if len(self.stacks) else None\n",
" num_stacks = len(self.stacks)\n", " num_stacks = len(self.stacks)\n",
" if num_stacks == 0:\n",
" self.last_stack = None\n",
" else:\n",
" self.last_stack = self.stacks[num_stacks-1]\n",
" else:\n",
" data = self.last_stack.pop()\n",
" return data" " return data"
] ]
}, },
@@ -194,8 +188,7 @@
"\n", "\n",
" def test_set_of_stacks(self):\n", " def test_set_of_stacks(self):\n",
" print('Test: Push on an empty stack')\n", " print('Test: Push on an empty stack')\n",
" capacity = 2\n", " stacks = SetOfStacks(capacity=2)\n",
" stacks = SetOfStacks(capacity)\n",
" stacks.push(3)\n", " stacks.push(3)\n",
"\n", "\n",
" print('Test: Push on a non-empty stack')\n", " print('Test: Push on a non-empty stack')\n",
@@ -204,7 +197,7 @@
" print('Test: Push on a capacity stack to create a new one')\n", " print('Test: Push on a capacity stack to create a new one')\n",
" stacks.push('a')\n", " stacks.push('a')\n",
"\n", "\n",
" print('Test: Pop on a one element stack to destroy it')\n", " print('Test: Pop on a stack to destroy it')\n",
" assert_equal(stacks.pop(), 'a')\n", " assert_equal(stacks.pop(), 'a')\n",
"\n", "\n",
" print('Test: Pop general case')\n", " print('Test: Pop general case')\n",
@@ -240,7 +233,7 @@
"Test: Push on an empty stack\n", "Test: Push on an empty stack\n",
"Test: Push on a non-empty stack\n", "Test: Push on a non-empty stack\n",
"Test: Push on a capacity stack to create a new one\n", "Test: Push on a capacity stack to create a new one\n",
"Test: Pop on a one element stack to destroy it\n", "Test: Pop on a stack to destroy it\n",
"Test: Pop general case\n", "Test: Pop general case\n",
"Test: Pop on no elements\n", "Test: Pop on no elements\n",
"Success: test_set_of_stacks\n" "Success: test_set_of_stacks\n"
@@ -254,21 +247,21 @@
], ],
"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,

5
stacks_queues/set_of_stacks/test_set_of_stacks.py
View File

@@ -5,8 +5,7 @@ class TestSetOfStacks(object):
def test_set_of_stacks(self): def test_set_of_stacks(self):
print('Test: Push on an empty stack') print('Test: Push on an empty stack')
capacity = 2 stacks = SetOfStacks(capacity=2)
stacks = SetOfStacks(capacity)
stacks.push(3) stacks.push(3)
print('Test: Push on a non-empty stack') print('Test: Push on a non-empty stack')
@@ -15,7 +14,7 @@ class TestSetOfStacks(object):
print('Test: Push on a capacity stack to create a new one') print('Test: Push on a capacity stack to create a new one')
stacks.push('a') stacks.push('a')
print('Test: Pop on a one element stack to destroy it') print('Test: Pop on a stack to destroy it')
assert_equal(stacks.pop(), 'a') assert_equal(stacks.pop(), 'a')
print('Test: Pop general case') print('Test: Pop general case')