# 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 Heap queue algorithm. Go to the editor

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

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

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4. Write a Python function which accepts an arbitrary list and converts it to a heap using Heap queue algorithm. Go to the editor

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5. Write a Python program to delete the smallest element from the given Heap and then inserts a new item. Go to the editor

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6. Write a Python program to sort a given list of elements in ascending order using Heap queue algorithm. Go to the editor

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7. Write a Python program to find the kth (1 <= k <= array's length) largest element in an unsorted array using Heap queue algorithm. Go to the editor

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8. Write a Python program to compute maximum product of three numbers of a given array of integers using Heap queue algorithm. Go to the editor

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9. Write a Python program to find the top k integers that occur the most frequently from a given lists of sorted and distinct integers using Heap queue algorithm. Go to the editor

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10. Write a Python program to get the n expensive and cheap price items from a given dataset using Heap queue algorithm. Go to the editor

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11. Write a Python program to merge multiple sorted inputs into a single sorted iterator (over the sorted values) using Heap queue algorithm. Go to the editor

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12. Given a n x n matrix where each of the rows and columns are sorted in ascending order, write a Python program to find the kth smallest element in the matrix. Go to the editor

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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 Heap queue algorithm. Go to the editor

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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 Heap queue algorithm. Go to the editor

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15. Write a Python program to check if the letters of a given string can be rearranged so that two characters that are adjacent to each other are different using Heap queue algorithm. Go to the editor

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16. Write a Python program which add integer numbers from the data stream to a heapq and compute the median of all elements. Use Heap queue algorithm. Go to the editor

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17. You are given two integer arrays sorted in ascending order and an integer k. Write a Python program to find k number of pairs (u, v) which consists of one element from the first array and one element from the second array using Heap queue algorithm. Go to the editor

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18. Write a Python program to find the nth ugly number using Heap queue algorithm. Go to the editor

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19. Write a Python program to print a heap as a tree-like data structure. Go to the editor

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20. Write a Python program to combine two given sorted lists using heapq module. Go to the editor
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. Go to the editor
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. Go to the editor
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. Go to the editor
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. Go to the editor
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. Go to the editor
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 size of the queue. Go to the editor
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 whether a queue is empty or not. Go to the editor
Sample Output:
True
False

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28. Write a Python program to create a FIFO queue. Go to the editor
Sample Output:
0 1 2 3

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29. Write a Python program to create a LIFO queue. Go to the editor
Sample Output:
3 2 1 0

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Python Code Editor:

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## Python: Tips of the Day

Simplify the way you collapse nested lists:

```x = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9]
]
x
```

Output:

```[[1, 2, 3], [4, 5, 6], [7, 8, 9]]
```
```result = []
for sublist in x:
for item in sublist:
result.append(item)
result
```

Output:

```[1, 2, 3, 4, 5, 6, 7, 8, 9]
```
`[item for sublist in x for item in sublist]`

Output:

```[1, 2, 3, 4, 5, 6, 7, 8, 9]
```
```import itertools
itertools.chain(*x)
```

Output:

```<itertools.chain at 0x1dd5fb60320>
```
`list(itertools.chain(*x))`

Output:

```[1, 2, 3, 4, 5, 6, 7, 8, 9]
```