Question

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].

Analyze


Solution

class Solution {
public:
    int rotatedDigits(int N) {
      int res = 0;
      for (int i = 0; i <= N; ++i) {
        if( isRotatedDigits(i) ) ++res;
      }
      return res;
    }
    bool isRotatedDigits(int number) {
      int digit = 0;
      bool good_flag = false;
      while(number) {
        digit = number % 10;
        if(number) number = number / 10; 
        if (digit == 3 || digit == 4 || digit == 7) return false;
        else if (digit == 0 || digit == 1 || digit == 8 ) continue;
        else {
          good_flag = true;
        }
      }
      return good_flag;
    }
};
By guozetang            Updated: 2020-09-19 13:02:30

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