# Python: heap queue algorithm - Exercises, Practice, Solution

## Python heap queue algorithm [29 exercises with solution ]

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Heaps are binary trees for which every parent node has a value less than or equal to any of its children.

Here are some exercises of heap queue algorithm.

**1.** Write a Python program to find the three largest integers from a given list of numbers using the heap queue algorithm.

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**2.** Write a Python program to find the three smallest integers from a given list of numbers using the heap queue algorithm.

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**3.** Write a Python program to implement heapsort by pushing all values onto a heap and then popping off the smallest values one at a time.

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**4.** Write a Python function that accepts an arbitrary list and converts it to a heap using the heap queue algorithm.

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**5.** Write a Python program that deletes the smallest element from a heap and then inserts a new item.

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**6.** Write a Python program to sort a given list of elements in ascending order using the heap queue algorithm.

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**7.** Write a Python program to find the k^{th} (1 <= k <= array's length) largest element in an unsorted array using the heap queue algorithm.

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**8.** Write a Python program to compute the maximum product of three numbers in a given array of integers using the heap queue algorithm.

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**9.** Write a Python program to find the top k integers that occur the most frequently from a given list of sorted and distinct integers using the heap queue algorithm.

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**10.** Write a Python program to get the most expensive and least expensive items from a given dataset using the heap queue algorithm.

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**11.** Write a Python program that merges multiple sorted inputs into a single sorted iterator (over the sorted values) using the heap queue algorithm.

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**12.** Given a n x n matrix where each of the rows and columns is sorted in ascending order, write a Python program to find the kth smallest element in the matrix using the heap queue algorithm.

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**13.** Write a Python program to find the nth super ugly number from a given prime list of size k using the heap queue algorithm.

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**14.** Write a Python program to get the k most frequent elements from a given non-empty list of words using the heap queue algorithm

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**15.** Write a Python program to check if the letters in a given string can be rearranged. This is to make sure that two characters that are adjacent to each other are different using the heap queue algorithm.

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**16.** Write a Python program that adds integer numbers from the data stream to a heapq and computes the median of all elements. Use the heap queue algorithm.

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**17.** You have two integer arrays sorted in ascending order and an integer k. Write a Python program to find k number of pairs (u, v) which consist of one element from the first array and one element from the second array using the heap queue algorithm.

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**18.** Write a Python program to find the n^{th} ugly number using the heap queue algorithm.

Sample Output:

7th Ugly number:

8

10th Ugly number:

12

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**19.** Write a Python program to print a heap as a tree-like data structure.

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**20.** Write a Python program to combine two sorted lists using the heapq module.

Sample Output:

Original sorted lists:

[1, 3, 5, 7, 9, 11]

[0, 2, 4, 6, 8, 10]

After merging the said two sorted lists:

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

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**21.** Write a Python program to push three items into the heap and print the items from the heap.

Sample Output:

('V', 1)

('V', 2)

('V', 3)

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**22.** Write a Python program to push three items into a heap and return the smallest item from the heap. Also, pop and return the smallest item from the heap.

Sample Output:

Items in the heap:

('V', 1)

('V', 3)

('V', 2)

----------------------

The smallest item in the heap:

('V', 1)

----------------------

Pop the smallest item in the heap:

('V', 2)

('V', 3)

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**23.** Write a Python program to push an item on the heap, then pop and return the smallest item from the heap.

Sample Output:

Items in the heap:

('V', 1)

('V', 3)

('V', 2)

----------------------

Using heappushpop push item on the heap and return the smallest item.

('V', 2)

('V', 3)

('V', 6)

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**24.** Write a Python program to create a heapsort, pushing all values onto a heap and then popping off the smallest values one at a time.

Sample Output:

[10, 20, 20, 40, 50, 50, 60, 70, 80, 90, 100]

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**25.** Write a Python program to get the two largest and three smallest items from a dataset.

Sample Output:

[100, 90]
[10, 20, 20]

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**26.** Write a Python program to create a queue and display all the members and the size of the queue.

Sample Output:

Members of the queue:

0 1 2 3

Size of the queue:

4

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**27.** Write a Python program to find out whether a queue is empty or not.

Sample Output:

True

False

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**28.** Write a Python program to create a FIFO queue.

Sample Output:

0 1 2 3

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**29.** Write a Python program to create a LIFO queue.

Sample Output:

3 2 1 0

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## Python: Tips of the Day

**Combining Lists Using Zip:**

- Takes multiple collections and returns a new collection.
- The new collection contains items where each item contains one element from each input collection.
- It allows us to transverse multiple collections at the same time.

name = 'abcdef' suffix = [1,2,3,4,5,6] zip(name, suffix) --> returns (a,1),(b,2),(c,3),(d,4),(e,5),(f,6)

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