Java Program to Find Maximum value possible by rotating digits of a given number

Last Updated : 27 Jan, 2022

Given a positive integer N, the task is to find the maximum value among all the rotations of the digits of the integer N.

Examples:

Input: N = 657
Output: 765
Explanation: All rotations of 657 are {657, 576, 765}. The maximum value among all these rotations is 765.

Input: N = 7092
Output: 9270
Explanation:
All rotations of 7092 are {7092, 2709, 9270, 0927}. The maximum value among all these rotations is 9270.

Approach: The idea is to find all rotations of the number N and print the maximum among all the numbers generated. Follow the steps below to solve the problem:

Count the number of digits present in the number N, i.e. upper bound of log₁₀N.
Initialize a variable, say ans with the value of N, to store the resultant maximum number generated.
Iterate over the range [1, log₁₀(N) - 1] and perform the following steps:
- Update the value of N with its next rotation.
- Now, if the next rotation generated exceeds ans, then update ans with the rotated value of N
After completing the above steps, print the value of ans as the required answer.

Below is the implementation of the above approach:

Java

// Java program for the above approach
import java.util.*;
class GFG
{

// Function to find the maximum value
// possible by rotations of digits of N
static void findLargestRotation(int num)
{
  
    // Store the required result
    int ans = num;

    // Store the number of digits
    int len = (int)Math.floor(((int)Math.log10(num)) + 1);
    int x = (int)Math.pow(10, len - 1);

    // Iterate over the range[1, len-1]
    for (int i = 1; i < len; i++) {

        // Store the unit's digit
        int lastDigit = num % 10;

        // Store the remaining number
        num = num / 10;

        // Find the next rotation
        num += (lastDigit * x);

        // If the current rotation is
        // greater than the overall
        // answer, then update answer
        if (num > ans) {
            ans = num;
        }
    }

    // Print the result
    System.out.print(ans);
}

// Driver Code
public static void main(String[] args)
{
    int N = 657;
    findLargestRotation(N);
}
}

// This code is contributed by sanjoy_62.