The max value in the max heap isn't the correct value
Question:
The program takes as input:
(string)’yyyy-mm-dd’, (int)sensor id, (int)covid level.
The expected output is: yyyy-mm-dd,covid level.
Input: 2022−09−08, 23, 371; 2022−09−08, 2, 3171; 2022−09−08, 12, 43; 2021−03−21, 4, 129
Output: 2022 −09 −08, 3171
I have provided my code below. My output doesn’t work correctly when the input is large. I think the heapify got screwed up somewhere. Here is my code:
import sys
class MaxHeap:
def __init__(self, maxsize):
self.maxsize = maxsize
self.size = 0
self.Heap = [0] * (self.maxsize + 1)
self.Heap[0] = ('1.1.1977', sys.maxsize)
self.FRONT = 1
# Function to return the position of parent for the node currently at pos
def parent(self, pos):
return pos // 2
# Function to return the position of the left child for the node currently at pos
def leftChild(self, pos):
return 2 * pos
# Function to return the position of the right child for the node currently at pos
def rightChild(self, pos):
return (2 * pos) + 1
# Function that returns true if the passed node is a leaf node
def isLeaf(self, pos):
if pos >= (self.size//2) and pos <= self.size:
return True
return False
# Function to swap two nodes of the heap
def swap(self, fpos, spos):
self.Heap[fpos], self.Heap[spos] = (self.Heap[spos], self.Heap[fpos])
# Function to heapify the node at pos
def maxHeapify(self, pos):
# If the node is a non-leaf node and smaller
# than any of its child
if not self.isLeaf(pos):
if (self.Heap[pos] < self.Heap[self.leftChild(pos)] or self.Heap[pos] < self.Heap[self.rightChild(pos)]):
# Swap with the left child and heapify
# the left child
if (self.Heap[self.leftChild(pos)] > self.Heap[self.rightChild(pos)]):
self.swap(pos, self.leftChild(pos))
self.maxHeapify(self.leftChild(pos))
# Swap with the right child and heapify
# the right child
else:
self.swap(pos, self.rightChild(pos))
self.maxHeapify(self.rightChild(pos))
# Function to insert a node into the heap
def insert(self, element):
if self.size >= self.maxsize:
return
self.size += 1
self.Heap[self.size] = element
current = self.size
while (str(self.Heap[current]) >
str(self.Heap[self.parent(current)])):
self.swap(current, self.parent(current))
current = self.parent(current)
# Function to print the contents of the heap
def Print(self):
for i in range(1, (self.size // 2) + 1):
print("PARENT : " + str(self.Heap[i]) +
"LEFT CHILD : " + str(self.Heap[2 * i]) +
"RIGHT CHILD : " + str(self.Heap[(2 * i) + 1]))
# Function to remove and return the maximum
# element from the heap
def extractMax(self):
ext = self.Heap[self.FRONT]
self.Heap[self.FRONT] = self.Heap[self.size]
self.size -= 1
self.maxHeapify(self.FRONT)
return ext
# Driver Code
if __name__ == "__main__":
input = input()
input = input.split(";")
dates = []
values = []
for d in input:
date = d.split(',', 2)
dates.append(date[0])
values.append(date[2])
values = [int(x) for x in values]
tuples = list(zip(dates, values))
heap = MaxHeap(len(tuples) + 1)
for t in tuples:
heap.insert(t)
max_heap = heap.extractMax()
My output for this input:
2023-04-19,9132,438804;2022-04-04,4535,316300;2021-05-24,3079,101563;2021-04-29,7378,18098;2023-04-13,7790,15956;2023-08-16,4086,190312;2022-05-07,6779,749569;2021-07-06,9852,574634;2022-09-23,934,112247;2022-01-31,8810,405090;2020-12-22,7342,381167;2021-07-17,711,993694;2022-10-10,409,522123;2021-03-31,3392,797680;2021-04-19,5982,842608;2023-05-01,2400,487512;2021-09-20,945,842398;2020-01-18,9269,104747;2020-07-26,6781,596629;2021-08-02,8162,360261;2019-09-30,1919,637237;2022-12-06,1914,81688;2022-07-13,603,676273;2022-05-27,950,185217;2022-04-25,3386,595046;2020-04-24,4442,779015;2020-11-10,2985,366614;2021-09-08,9104,797580;2021-07-09,4635,890720;2023-01-12,7299,514824;2023-08-26,5111,261446;2022-11-30,9761,664774;2023-02-27,5702,101817;2022-10-30,7463,552832;2020-05-26,8611,635344;2020-01-10,1154,912487;2021-08-03,1751,481369;2020-09-23,5469,696646;2021-11-07,6329,836149;2022-05-18,8444,621113;2021-09-15,5352,128613;2023-07-01,6008,393441;2022-10-11,2598,346254;2019-12-18,1956,666816;2020-10-01,5303,705215;2022-12-06,3580,86464;2021-08-19,655,503907;2020-07-27,9448,414938;2021-05-29,1887,10723;2023-05-30,3787,753166;2021-04-25,615,155563;2022-07-06,5024,504939;2020-07-10,9029,980440;2020-08-21,6138,862944;2020-07-14,2660,648708;2023-05-13,5482,313792;2020-01-21,3730,401475;2022-01-23,1701,569155;2021-05-10,6324,361397;2020-07-09,7832,553689;2020-01-08,7655,261610;2022-06-23,6407,300140;2020-02-28,4394,120407;2022-01-15,8922,372324;2020-06-01,2544,903305;2021-07-18,4792,571747;2020-08-29,8251,72353;2019-09-09,4894,886404;2021-06-27,473,446021;2021-03-12,7044,711193;2020-01-11,9889,188949;2021-07-11,8809,667911;2021-04-16,7349,103581;2021-08-03,966,328995;2023-07-08,4301,48755;2022-03-20,7034,228660;2020-09-08,4874,860249;2022-03-18,3717,107146;2023-05-01,3596,582978;2022-08-02,2420,2761;2022-09-10,3728,672878;2019-12-15,2545,251375;2022-10-26,1526,376646;2021-08-29,6201,158015;2022-04-02,972,843280;2020-12-01,1891,424955;2022-10-24,7948,563497;2021-07-16,7922,901972;2023-02-01,464,870315;2020-03-29,3974,512011;2023-02-04,915,131894;2023-06-02,1889,971126;2022-01-19,7300,245778;2020-01-18,5677,154759;2023-01-20,1373,152443;2022-09-29,2471,417724;2022-09-09,2260,504994;2023-08-30,9896,425287;2021-07-16,3388,607646;2021-03-13,4559,207877;2022-09-08,42,114573
is: 2023-08-30,425287
It’s supposed to be: 2021-07-17,993694
Could someone please help me? I’ve fixated on this question for way too long now.
Answers:
The problem is your sorting. You are sorting based on date. If you change your loop inside insert to this, you’ll sort by the numeric value and things work fine:
while self.Heap[current][1] > self.Heap[self.parent(current)][1]:
The program takes as input:
(string)’yyyy-mm-dd’, (int)sensor id, (int)covid level.
The expected output is: yyyy-mm-dd,covid level.
Input: 2022−09−08, 23, 371; 2022−09−08, 2, 3171; 2022−09−08, 12, 43; 2021−03−21, 4, 129
Output: 2022 −09 −08, 3171
I have provided my code below. My output doesn’t work correctly when the input is large. I think the heapify got screwed up somewhere. Here is my code:
import sys
class MaxHeap:
def __init__(self, maxsize):
self.maxsize = maxsize
self.size = 0
self.Heap = [0] * (self.maxsize + 1)
self.Heap[0] = ('1.1.1977', sys.maxsize)
self.FRONT = 1
# Function to return the position of parent for the node currently at pos
def parent(self, pos):
return pos // 2
# Function to return the position of the left child for the node currently at pos
def leftChild(self, pos):
return 2 * pos
# Function to return the position of the right child for the node currently at pos
def rightChild(self, pos):
return (2 * pos) + 1
# Function that returns true if the passed node is a leaf node
def isLeaf(self, pos):
if pos >= (self.size//2) and pos <= self.size:
return True
return False
# Function to swap two nodes of the heap
def swap(self, fpos, spos):
self.Heap[fpos], self.Heap[spos] = (self.Heap[spos], self.Heap[fpos])
# Function to heapify the node at pos
def maxHeapify(self, pos):
# If the node is a non-leaf node and smaller
# than any of its child
if not self.isLeaf(pos):
if (self.Heap[pos] < self.Heap[self.leftChild(pos)] or self.Heap[pos] < self.Heap[self.rightChild(pos)]):
# Swap with the left child and heapify
# the left child
if (self.Heap[self.leftChild(pos)] > self.Heap[self.rightChild(pos)]):
self.swap(pos, self.leftChild(pos))
self.maxHeapify(self.leftChild(pos))
# Swap with the right child and heapify
# the right child
else:
self.swap(pos, self.rightChild(pos))
self.maxHeapify(self.rightChild(pos))
# Function to insert a node into the heap
def insert(self, element):
if self.size >= self.maxsize:
return
self.size += 1
self.Heap[self.size] = element
current = self.size
while (str(self.Heap[current]) >
str(self.Heap[self.parent(current)])):
self.swap(current, self.parent(current))
current = self.parent(current)
# Function to print the contents of the heap
def Print(self):
for i in range(1, (self.size // 2) + 1):
print("PARENT : " + str(self.Heap[i]) +
"LEFT CHILD : " + str(self.Heap[2 * i]) +
"RIGHT CHILD : " + str(self.Heap[(2 * i) + 1]))
# Function to remove and return the maximum
# element from the heap
def extractMax(self):
ext = self.Heap[self.FRONT]
self.Heap[self.FRONT] = self.Heap[self.size]
self.size -= 1
self.maxHeapify(self.FRONT)
return ext
# Driver Code
if __name__ == "__main__":
input = input()
input = input.split(";")
dates = []
values = []
for d in input:
date = d.split(',', 2)
dates.append(date[0])
values.append(date[2])
values = [int(x) for x in values]
tuples = list(zip(dates, values))
heap = MaxHeap(len(tuples) + 1)
for t in tuples:
heap.insert(t)
max_heap = heap.extractMax()
My output for this input:
2023-04-19,9132,438804;2022-04-04,4535,316300;2021-05-24,3079,101563;2021-04-29,7378,18098;2023-04-13,7790,15956;2023-08-16,4086,190312;2022-05-07,6779,749569;2021-07-06,9852,574634;2022-09-23,934,112247;2022-01-31,8810,405090;2020-12-22,7342,381167;2021-07-17,711,993694;2022-10-10,409,522123;2021-03-31,3392,797680;2021-04-19,5982,842608;2023-05-01,2400,487512;2021-09-20,945,842398;2020-01-18,9269,104747;2020-07-26,6781,596629;2021-08-02,8162,360261;2019-09-30,1919,637237;2022-12-06,1914,81688;2022-07-13,603,676273;2022-05-27,950,185217;2022-04-25,3386,595046;2020-04-24,4442,779015;2020-11-10,2985,366614;2021-09-08,9104,797580;2021-07-09,4635,890720;2023-01-12,7299,514824;2023-08-26,5111,261446;2022-11-30,9761,664774;2023-02-27,5702,101817;2022-10-30,7463,552832;2020-05-26,8611,635344;2020-01-10,1154,912487;2021-08-03,1751,481369;2020-09-23,5469,696646;2021-11-07,6329,836149;2022-05-18,8444,621113;2021-09-15,5352,128613;2023-07-01,6008,393441;2022-10-11,2598,346254;2019-12-18,1956,666816;2020-10-01,5303,705215;2022-12-06,3580,86464;2021-08-19,655,503907;2020-07-27,9448,414938;2021-05-29,1887,10723;2023-05-30,3787,753166;2021-04-25,615,155563;2022-07-06,5024,504939;2020-07-10,9029,980440;2020-08-21,6138,862944;2020-07-14,2660,648708;2023-05-13,5482,313792;2020-01-21,3730,401475;2022-01-23,1701,569155;2021-05-10,6324,361397;2020-07-09,7832,553689;2020-01-08,7655,261610;2022-06-23,6407,300140;2020-02-28,4394,120407;2022-01-15,8922,372324;2020-06-01,2544,903305;2021-07-18,4792,571747;2020-08-29,8251,72353;2019-09-09,4894,886404;2021-06-27,473,446021;2021-03-12,7044,711193;2020-01-11,9889,188949;2021-07-11,8809,667911;2021-04-16,7349,103581;2021-08-03,966,328995;2023-07-08,4301,48755;2022-03-20,7034,228660;2020-09-08,4874,860249;2022-03-18,3717,107146;2023-05-01,3596,582978;2022-08-02,2420,2761;2022-09-10,3728,672878;2019-12-15,2545,251375;2022-10-26,1526,376646;2021-08-29,6201,158015;2022-04-02,972,843280;2020-12-01,1891,424955;2022-10-24,7948,563497;2021-07-16,7922,901972;2023-02-01,464,870315;2020-03-29,3974,512011;2023-02-04,915,131894;2023-06-02,1889,971126;2022-01-19,7300,245778;2020-01-18,5677,154759;2023-01-20,1373,152443;2022-09-29,2471,417724;2022-09-09,2260,504994;2023-08-30,9896,425287;2021-07-16,3388,607646;2021-03-13,4559,207877;2022-09-08,42,114573
is: 2023-08-30,425287
It’s supposed to be: 2021-07-17,993694
Could someone please help me? I’ve fixated on this question for way too long now.
The problem is your sorting. You are sorting based on date. If you change your loop inside insert to this, you’ll sort by the numeric value and things work fine:
while self.Heap[current][1] > self.Heap[self.parent(current)][1]: