2553. Separate the Digits in an Array

Problem

Given an array of positive integers nums, return **an array *answer* that consists of the digits of each integer in nums after separating them in the same order they appear in **nums.

To separate the digits of an integer is to get all the digits it has in the same order.

• For example, for the integer 10921, the separation of its digits is [1,0,9,2,1].

  Example 1:

Input: nums = [13,25,83,77]
Output: [1,3,2,5,8,3,7,7]
Explanation: 
- The separation of 13 is [1,3].
- The separation of 25 is [2,5].
- The separation of 83 is [8,3].
- The separation of 77 is [7,7].
answer = [1,3,2,5,8,3,7,7]. Note that answer contains the separations in the same order.

Example 2:

Input: nums = [7,1,3,9]
Output: [7,1,3,9]
Explanation: The separation of each integer in nums is itself.
answer = [7,1,3,9].

  Constraints:

• 1 <= nums.length <= 1000

• 1 <= nums[i] <= 105

Solution (Java)

class Solution {
    public int[] separateDigits(int[] nums) {
       List<Integer> ans = new ArrayList<>();
        for (int num : nums) {
            List<Integer> temp = new ArrayList<>();
            while (num > 0) {
                temp.add(num % 10);
                num /= 10;
            }
            for (int j = temp.size() - 1; j >= 0; j--) {
                ans.add(temp.get(j));
            }
        }
        int[] result = new int[ans.size()];
        for (int i = 0; i < ans.size(); i++) {
            result[i] = ans.get(i);
        }
        return result;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).