[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:

• 0, 1, 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