3754. Concatenate Non-Zero Digits and Multiply by Sum I

Description

You are given an integer n.

Form a new integer x by concatenating all the non-zero digits of n in their original order. If there are no non-zero digits, x = 0.

Let sum be the sum of digits in x.

Return an integer representing the value of x * sum.

 

Example 1:

Input: n = 10203004

Output: 12340

Explanation:

• The non-zero digits are 1, 2, 3, and 4. Thus, x = 1234.
• The sum of digits is sum = 1 + 2 + 3 + 4 = 10.
• Therefore, the answer is x * sum = 1234 * 10 = 12340.

Example 2:

Input: n = 1000

Output: 1

Explanation:

• The non-zero digit is 1, so x = 1 and sum = 1.
• Therefore, the answer is x * sum = 1 * 1 = 1.

 

Constraints:

• 0 <= n <= 109

 

Solutions

Solution: Math

• Time complexity: O(logn)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number} n
 * @return {number}
 */
const sumAndMultiply = function (n) {
  let x = 0;
  let pos = 0;
  let sum = 0;

  while (n) {
    const digit = n % 10;

    if (digit) {
      x += digit * 10 ** pos;
      pos += 1;
      sum += digit;
    }

    n = Math.floor(n / 10);
  }

  return x * sum;
};