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Reversing a Number

Reversing the digits of a number by extracting the last digit and appending it to a running reversed number.

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We can reuse the digit-extraction algorithm, just that now instead of extracting digits we append them to a reversed number.

Reversing a number

Algorithm:

  1. Initialize an integer revNum to 0. This will store the reversed number.
  2. Iterate while the input integer n is greater than 0.
  3. Calculate the last digit using the modulus operator (n % 10) and store it in lastDigit.
  4. Remove the last digit from the input integer by dividing it by 10.
  5. Update the reversed number: revNum = (revNum * 10) + lastDigit. This appends the last digit to the end of the reversed number.
  6. After exiting the loop, return the reversed number.
public class Main {
    public static void reverse(int n) {
        // Initialize a variable 'revNum' to
        // store the reverse of the input integer.
        int revNum = 0;
        // Start a while loop to reverse the
        // digits of the input integer.
        while(n > 0){
            // Extract the last digit of
            // 'n' and store it in 'ld'.
            int ld = n % 10;


            // Remove the last digit from 'n'.
            n = n / 10;


            // Multiply the current reverse number
            // by 10 and add the last digit.
            revNum = (revNum * 10) + ld;
        }
        // Print the reversed number.
        System.out.println(revNum);
    }
}