solves #2553: Separate the Digits in an Array in java

Author: anishLearnsToCode

README.md

@@ -798,7 +798,7 @@
 | 2540 | [Minimum Common Value](https://leetcode.com/problems/minimum-common-value)                                                                                             |                                                                                     [![Java](assets/java.png)](src/MinimumCommonValue.java)                                                                                      |                                                                                                                                   |
 | 2544 | [Alternating Digit Sum](https://leetcode.com/problems/alternating-digit-sum)                                                                                           |                                                                                     [![Java](assets/java.png)](src/AlternatingDigitSum.java)                                                                                     |                                                                                                                                   |
 | 2549 | [Count Distinct Numbers on Board](https://leetcode.com/problems/count-distinct-numbers-on-board)                                                                       |                                                                                 [![Java](assets/java.png)](src/CountDistinctNumbersOnBoard.java)                                                                                 |                                                                                                                                   |
-| 2553 | [Separate the Digits in an Array](https://leetcode.com/problems/separate-the-digits-in-an-array)                                                                       |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 2553 | [Separate the Digits in an Array](https://leetcode.com/problems/separate-the-digits-in-an-array)                                                                       |                                                                                 [![Java](assets/java.png)](src/SeparateTheDigitsInAnArray.java)                                                                                  |                                                                                                                                   |
 | 2558 | [Take Gifts From the Richest Pile](https://leetcode.com/problems/take-gifts-from-the-richest-pile)                                                                     |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2562 | [Find the Array Concatenation Value](https://leetcode.com/problems/find-the-array-concatenation-value)                                                                 |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2566 | [Maximum Difference by Remapping a Digit](https://leetcode.com/problems/maximum-difference-by-remapping-a-digit)                                                       |                                                                                                                                                                                                                                  |                                                                                                                                   |

src/SeparateTheDigitsInAnArray.java

@@ -0,0 +1,31 @@
+// https://leetcode.com/problems/separate-the-digits-in-an-array
+// T: O(N)
+// S: O(N)
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class SeparateTheDigitsInAnArray {
+    public int[] separateDigits(int[] nums) {
+        final List<Integer> digits = new ArrayList<>();
+        for (int number : nums) {
+            addDigitsToList(digits, number);
+        }
+        return toArray(digits);
+    }
+
+    private int[] toArray(List<Integer> list) {
+        final int[] array = new int[list.size()];
+        for (int index = 0 ; index < list.size() ; index++) {
+            array[index] = list.get(index);
+        }
+        return array;
+    }
+
+    private void addDigitsToList(List<Integer> digits, int number) {
+        final String num = number + "";
+        for (int index = 0 ; index < num.length() ; index++) {
+            digits.add(num.charAt(index) - '0');
+        }
+    }
+}