# Python: Find the nth ugly number using Heap queue algorithm

## Python heap queue algorithm: Exercise-18 with Solution

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

Ugly numbers are positive numbers whose only prime factors are 2, 3 or 5. The sequence 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, ... shows the first 10 ugly numbers.

Note: 1 is typically treated as an ugly number.

**Sample Solution**:

**Python Code:**

```
import heapq
class Solution(object):
#:type n: integer
#:return type: integer
def nth_Ugly_Number(self, n):
ugly_num = 0
heap = []
heapq.heappush(heap, 1)
for _ in range(n):
ugly_num = heapq.heappop(heap)
if ugly_num % 2 == 0:
heapq.heappush(heap, ugly_num * 2)
elif ugly_num % 3 == 0:
heapq.heappush(heap, ugly_num * 2)
heapq.heappush(heap, ugly_num * 3)
else:
heapq.heappush(heap, ugly_num * 2)
heapq.heappush(heap, ugly_num * 3)
heapq.heappush(heap, ugly_num * 5)
return ugly_num
n = 7
S = Solution()
result = S.nth_Ugly_Number(n)
print("7th Ugly number:")
print(result)
n = 10
result = S.nth_Ugly_Number(n)
print("\n10th Ugly number:")
print(result)
```

Sample Output:

7th Ugly number: 8 10th Ugly number: 12

**Flowchart:**

**Python Code Editor:**

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**Previous: ** 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.

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

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