Program to find all upside down numbers of length n in Python

Suppose we have a value n. We have to find all upside down numbers of length n. As we knot the upside down number is one that appears the same when flipped 180 degrees.

So, if the input is like n = 2, then the output will be ['11', '69', '88', '96'].

To solve this, we will follow these steps −

• Define a function middle() . This will take x

• if x is 0, then

  • return list of a blank string

• if x is same as 1, then

  • return a new list of elements 0, 1, 8

• ret := a new list

• mid := middle(x − 2)

• for each m in mid, do

  • if x is not same as n, then

    • insert ("0" concatenate m concatenate "0") at the end of ret

  • insert ("1" concatenate m concatenate "1") at the end of ret

  • insert ("6" concatenate m concatenate "9") at the end of ret

  • insert ("8" concatenate m concatenate "8") at the end of ret

  • insert ("9" concatenate m concatenate "6") at the end of ret

• return ret

• From the main method, do the following −

• if n is 0, then

  • return a new list

• otherwise return sorted list of middle(n)

Let us see the following implementation to get better understanding −

Example

 Live Demo

class Solution:
   def solve(self, n):
      if not n:
         return []
      def middle(x=n):
         if not x:
            return [""]
         if x == 1:
            return list("018")
         ret = []
         mid = middle(x - 2)
         for m in mid:
            if x != n:
               ret.append("0" + m + "0")
            ret.append("1" + m + "1")
            ret.append("6" + m + "9")
            ret.append("8" + m + "8")
            ret.append("9" + m + "6")
         return ret
      return sorted(middle())
ob = Solution()
print(ob.solve(2))

Input

2

Output

['11', '69', '88', '96']

Arnab Chakraborty

Published on 21-Oct-2020 12:28:27

• Related Questions & Answers
• Binary Tree Upside Down in C++
• Finding the count of total upside down numbers in a range using JavaScript
• Program to find all missing numbers from 1 to N in Python
• Program to find sum of all odd length subarrays in Python
• Program to find sum of first N odd numbers in Python
• 8086 program to find average of n numbers
• Program to find the sum of first n odd numbers in Python
• Program to find length of longest matrix path length in Python
• All possible binary numbers of length n with equal sum in both halves?
• Program to find kth smallest n length lexicographically smallest string in python
• Program to find length of the longest path in an n-ary tree in Python
• Program to find maximum length of k ribbons of same length in Python
• Program to find lexicographically smallest lowercase string of length k and distance n in Python
• Program to find minimum length of lossy Run-Length Encoding in Python
• Program to find length of shortest supersequence in Python