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

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.