[Solved] An integer x is a good if after rotating each digit individually by 180 degrees, we get a valid number that is different from x. Each digit must be rotated – we cannot choose to leave it alone.

Question

An integer x is a good if after rotating each digit individually by 180 degrees, we get a valid number that is different from x. Each digit must be rotated – we cannot choose to leave it alone.

A number is valid if each digit remains a digit after rotation. For example:

  • 01, and 8 rotate to themselves,
  • 2 and 5 rotate to each other (in this case they are rotated in a different direction, in other words, 2 or 5 gets mirrored),
  • 6 and 9 rotate to each other, and
  • the rest of the numbers do not rotate to any other number and become invalid.

Given an integer n, return the number of good integers in the range [1, n].

Example 1:

Input: n = 10
Output: 4
Explanation: There are four good numbers in the range [1, 10] : 2, 5, 6, 9.
Note that 1 and 10 are not good numbers, since they remain unchanged after rotating.

Example 2:

Input: n = 1
Output: 0

Example 3:

Input: n = 2
Output: 1

Constraints:

  • 1 <= n <= 104

Python Solution

class Solution:
    def rotatedDigits(self, N: int) -> int:
        d = {'0':'0' , '1':'1' , '2':'5' , '8':'8' , '5':'2' , '6':'9' , '9':'6' }
        def checker(n):
            k=''
            for i in str(n):
                if i not in d.keys():
                    return False
                else:
                    k+=d[i]
            if k!=str(n):
                return True
            else:
                return False
        l=0
        for i in range(N+1):
            if checker(i):
                l+=1
        return l
Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

Articles: 520

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