Rotated Digits | String Problem | LeetCode 788
4 years ago Lalit Bhagtani 0
Problem Statement
A number N is a good number if after rotating each digit individually by 180 degrees, we get a valid number which is different from N.
A number is valid if each digit remains a digit after rotation. following is the list of digits and its rotated state.
0 --> 0 1 --> 1 2 --> 5 3 --> Invalid 4 --> Invalid 5 --> 2 6 --> 9 7 --> Invalid 8 --> 8 9 --> 6
Given a positive number N, find out how many numbers from 1 to N are good numbers.
Example
Input :- N = 12 Output :- 5
Input :- N = 21 Output :- 10
Solution
This problem can be solved in following steps :-
- Check each number from 1 to N.
- Check step 3 and 4 for each digit of the number.
- If number is made up of 3, 4 or 7 digit then number is not a good number.
- If number is made up of 2, 5, 6 or 9 digit (at least one occurrence of any one digit) and step 3 is false, then number is a good number.
Program
public class Main {
public static void main(String[] args) {
Main main = new Main();
int result = main.rotatedDigits(21);
System.out.println(result);
}
/* Solution */
public int rotatedDigits(int N) {
boolean isGood = false;
int num = 1, count = 0, x, rem;
while(num <= N){
isGood = false;
x = num;
while(x > 0){
rem = x %10;
x = x /10;
if(rem == 3 || rem == 4 || rem == 7){
isGood = false;
break;
}else if(rem == 2 || rem == 5 || rem == 6 || rem == 9){
isGood = true;
}
}
if(isGood){
count++;
}
num++;
}
return count;
}
}
Result
10
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