X is a good number 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. 0, 1, and 8 rotate to themselves; 2 and 5 rotate to each other; 6 and 9 rotate to each other, and the rest of the numbers do not rotate to any other number and become invalid.
Now given a positive number N
, how many numbers X from 1
to N
are good?
Example: Input: 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.
Note:
- N will be in range
[1, 10000]
.
class Solution(object): def rotatedDigits(self, N): """ :type N: int :rtype: int """ ans=0 for i in range(N): l=str(i+1) if '3' not in l and '4' not in l and '7' not in l: if '1' in l or '0' in l or '8' in l: if '2' in l or '5' in l or '6' in l or '9' in l: ans+=1 else: ans+=1 return ans