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:
[1, 10000].class Solution { public int rotatedDigits(int N) { int count = 0; for(int i =2;i<=N;i++){ if(Judge(i)){ count++; } } return count; } public Boolean Judge(int N){ Boolean b = true; int res=N; int dig=0; int NewNum =0; int t = 1; if (N<=10){ do{ dig = res%10; res = res/10; if(dig ==1 ||dig ==0 ||dig ==3 ||dig==4 ||dig ==7 ||dig ==8 ) return false; } while( res>0 ); return true; } else{ do { dig = res%10; res = res/10; if(dig ==3 ||dig==4 ||dig ==7 ) { return false; } else if( dig ==2) { dig = 5; } else if(dig ==5) { dig =2; } else if (dig ==6) { dig = 9; } else if(dig ==9) { dig =6; } NewNum = NewNum + dig*t; t = t*10; } while( res>0 ); if(NewNum !=N){ return true; } else{ return false; } } } }
(Medium) Good Number LeetCode - Mock Interview
原文：https://www.cnblogs.com/codingyangmao/p/11306500.html