Javascript Program to Rotate digits of a given number by K

Last Updated : 27 Jan, 2022

Given two integers N and K, the task is to rotate the digits of N by K. If K is a positive integer, left rotate its digits. Otherwise, right rotate its digits.

Examples:

Input: N = 12345, K = 2
Output: 34512
Explanation:
Left rotating N(= 12345) by K(= 2) modifies N to 34512.
Therefore, the required output is 34512

Input: N = 12345, K = -3
Output: 34512
Explanation:
Right rotating N(= 12345) by K( = -3) modifies N to 34512.
Therefore, the required output is 34512

Approach: Follow the steps below to solve the problem:

Initialize a variable, say X, to store the count of digits in N.
Update K = (K + X) % X to reduce it to a case of left rotation.
Remove the first K digits of N and append all the removed digits to the right of the digits of N.
Finally, print the value of N.

Below is the implementation of the above approach:

JavaScript

<script>
// Javascript program to implement
// the above approach

    // Function to find the count of
    // digits in N
    function numberOfDigit(N)
    {
 
        // Stores count of
        // digits in N
        let digit = 0;
 
        // Calculate the count
        // of digits in N
        while (N > 0) {
 
            // Update digit
            digit++;
 
            // Update N
            N = Math.floor( N / 10);
        }
        return digit;
    }
 
    // Function to rotate the digits of N by K
    function rotateNumberByK(N, K)
    {
 
        // Stores count of digits in N
        let X = numberOfDigit(N);
 
        // Update K so that only need to
        // handle left rotation
        K = ((K % X) + X) % X;
 
        // Stores first K digits of N
        let left_no = Math.floor (N / Math.floor(Math.pow(10,
                                         X - K)));
 
        // Remove first K digits of N
        N = N % Math.floor(Math.pow(10, X - K));
 
        // Stores count of digits in left_no
        let left_digit = numberOfDigit(left_no);
 
        // Append left_no to the right of
        // digits of N
        N = (N * Math.floor(Math.pow(10, left_digit)))
            + left_no;
 
        document.write(N);
    }

// Driver Code

    let N = 12345, K = 7;
 
        // Function Call
        rotateNumberByK(N, K);
  
  // This code is contributed by souravghosh0416.
</script>