788. Rotated Digits

Posted 2021-01-15 bernieloveslife

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:
    def rotatedDigits(self, N):
        """
        :type N: int
        :rtype: int
        """
        def judge(t):
            s = list(str(t))
            for i in range(len(s)):
                if s[i] in [‘3‘,‘4‘,‘7‘]:
                    return False
                if s[i]==‘2‘:
                    s[i] = ‘5‘
                    continue
                if s[i]==‘5‘:
                    s[i] = ‘2‘
                    continue
                if s[i]==‘6‘:
                    s[i] = ‘9‘
                    continue
                if s[i]==‘9‘:
                    s[i] = ‘6‘
                    continue
            if t == int(‘‘.join(s)):
                return False
            return True
        res = 0
        for i in range(1,N+1):
            if judge(i):
                # print(i)
                res += 1
        return res