Python: Get all strobogrammatic numbers that are of length n
Python Basic - 1: Exercise-17 with Solution
Write a Python program to get all strobogrammatic numbers that are of length n.
A strobogrammatic number is a number whose numeral is rotationally symmetric, so that it appears the same when rotated 180 degrees. In other words, the numeral looks the same right-side up and upside down (e.g., 69, 96, 1001).
For example,
Given n = 2, return ["11", "69", "88", "96"].
Given n = 3, return ['818', '111', '916', '619', '808', '101', '906', '609', '888', '181', '986', '689']
Pictorial Presentation:

Sample Solution:
Python Code:
#https://github.com/keon/algorithms/blob/master/math/generate_strobogrammtic.py
def gen_strobogrammatic(n):
"""
:type n: int
:rtype: List[str]
"""
result = helper(n, n)
return result
def helper(n, length):
if n == 0:
return [""]
if n == 1:
return ["1", "0", "8"]
middles = helper(n-2, length)
result = []
for middle in middles:
if n != length:
result.append("0" + middle + "0")
result.append("8" + middle + "8")
result.append("1" + middle + "1")
result.append("9" + middle + "6")
result.append("6" + middle + "9")
return result
print("n = 2: \n",gen_strobogrammatic(2))
print("n = 3: \n",gen_strobogrammatic(3))
print("n = 4: \n",gen_strobogrammatic(4))
Sample Output:
n = 2: ['88', '11', '96', '69'] n = 3: ['818', '111', '916', '619', '808', '101', '906', '609', '888', '181', '986', '689'] n = 4: ['8008', '1001', '9006', '6009', '8888', '1881', '9886', '6889', '8118', '1111', '9116', '6119', '8968', '1961', '9966', '6969', '8698', '1691', '9696', '6699']
Flowchart:

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Previous: Write a Python program to get the third side of right angled triangle from two given sides.
Next: Write a Python program to find the median among three given numbers.
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Python: Tips of the Day
What is the difference between Python's list methods append and extend?
append: Appends object at the end.
x = [1, 2, 3] x.append([4, 5]) print (x)
Output:
[1, 2, 3, [4, 5]]
extend: Extends list by appending elements from the iterable.
x = [1, 2, 3] x.extend([4, 5]) print (x)
Output:
[1, 2, 3, 4, 5]
Ref: https://bit.ly/2AZ6ZFq
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