class MinHeap: def __init__(self): #Filler for zeroth element to have the actual start of indexing to our min heap at arr[1] self.arr = [None]
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class MinHeap:
def __init__(self):
#Filler for zeroth element to have the actual start of indexing to our min heap at arr[1]
self.arr = [None]
self.size = 0
# Part A.
# Fill in the ff. functions such that, given an array implementation arr
# of a complete tree and a node at arr[idx], the following functions
# correctly return the indices of the left child, right child, and parent
# of the given node. Assume that the root node is at arr[1] (NOT arr[0]).
def _left_child(self, idx):
return __________ # Fill in the blank.
def _right_child(self, idx):
return __________ # Fill in the blank.
def _parent(self, idx):
return __________ # Fill in the blank.
def _swap_nodes(self, i, j):
'''Helper function for swapping two nodes at indices i and j.'''
self.arr[i], self.arr[j] = self.arr[j], self.arr[i]
def _bubble_down(self, idx):
'''
Bubbles down a node at arr[idx] to preserve min-heap properties.
Specifically, a node needs to be moved down the heap if its value is
greater than either of its children's values. To ensure that the
least node is at the top of the heap, the current node is swapped
with the lesser of its two children.
'''
# Part B.
# This is a standard implementation of a bubble down
# Modify this accordingly to accomodate Constraint #3 which indicates
# that you need to order alphabetically regardless of character case.
left_idx = self._left_child(idx)
right_idx = self._right_child(idx)
if (left_idx > self.size):
return
elif (right_idx > self.size):
left_val = self.arr[left_idx]
if (left_val < self.arr[idx]):
self._swap_nodes(left_idx, idx)
else:
left_val = self.arr[left_idx]
right_val = self.arr[right_idx]
if (left_val < self.arr[idx] and left_val < right_val):
self._swap_nodes(left_idx, idx)
self._bubble_down(left_idx)
elif (right_val < self.arr[idx] and right_val < left_val):
self._swap_nodes(right_idx, idx)
self._bubble_down(right_idx)
def _bubble_up(self, idx):
'''
Bubbles up a node at arr[idx] to preserve min-heap properties.
Specifically, a node needs to be moved up the heap if its value is
less than its parent's.
'''
# Part C.
# This is a standard implementation of a bubble up algorithm for min heap.
# Modify this accordingly to accomodate Constraint #3 which indicates
# that you need to order alphabetically regardless of character case.
parent_idx = self._parent(idx)
parent_val = self.arr[parent_idx]
if (idx == 1):
return
if (self.arr[idx] < parent_val):
self._swap_nodes(parent_idx, idx)
if (parent_idx > 1):
self._bubble_up(parent_idx)
# Part C.
# Complete the following function to perform the following operations:
# - pop the top node from the min-heap
# (i.e. remove the node and return its value)
# - swap nodes in the heap to preserve the heap's order and shape
# - adjust the count for the number of nodes in the heap
def extract(self):
'''Removes the minimum element from the heap and returns its value.'''
# Extract the results by doing something here. Hint: swap nodes and pop the array
result = _________
self.size = __________ # No. of nodes after the top node is popped
if (__________): # If the heap still contains nodes...
# --- Do something here. ---
return result
# Part D.
# Complete the following function to perform the following operations:
# - insert a new node (with value val) into the heap
# - swap nodes in the heap to preserve the heap's order and shape
# - adjust the count for the number of nodes in the heap
def insert(self, val):
'''Inserts a new value into the heap.'''
idx = __________ # Index where the new value should be placed
self.arr.insert(idx, val)
self.size = __________ # No. of nodes after insertion
if (__________): # If the new node is not the root...
# --- Do something here. ---
# NOTE: The following statements in main check for the correctness of
# your implementation. Do not modify anything beyond this point!
if __name__ == '__main__':
n = int(input())
ls = list()
for i in range(n):
ls.append(input().rstrip())
myHeap = MinHeap()
for x in ls:
myHeap.insert(x)
while(myHeap.size != 0):
print(myHeap.extract())
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