solves #2231: Largest Number After Digit Swaps by Parity in java

Author: anishLearnsToCode

Diff for: README.md

@@ -1,6 +1,6 @@
 # LeetCode Algorithms
 
-![problems-solved](https://img.shields.io/badge/Problems%20Solved-570/2081-1f425f.svg)
+![problems-solved](https://img.shields.io/badge/Problems%20Solved-593/2081-1f425f.svg)
 ![problems-solved-java](https://img.shields.io/badge/Java-556/2081-1abc9c.svg)
 ![problems-solved-python](https://img.shields.io/badge/Python-205/2081-1abc9c.svg)
 ![problems-solved-javascript](https://img.shields.io/badge/JavaScript-4/2081-1abc9c.svg)
@@ -725,7 +725,7 @@
 | 2220 | [Minimum Bit Flips to Convert Number](https://leetcode.com/problems/minimum-bit-flips-to-convert-number)                                                               |                                                                               [![Java](assets/java.png)](src/MinimumBitFlipsToConvertNumber.java)                                                                                |                                                                                                                                   |
 | 2224 | [Minimum Number of Operations to Convert Time](https://leetcode.com/problems/minimum-number-of-operations-to-convert-time)                                             |                                                                           [![Java](assets/java.png)](src/MinimumNumberOfOperationsToConvertTime.java)                                                                            |                                                                                                                                   |
 | 2229 | 🔒 [Check if an array is consecutive](https://leetcode.com/problems/check-if-an-array-is-consecutive)                                                                  |                                                                                                                                                                                                                                  |                                                                                                                                   |
-| 2231 | [Largest Number After Digit Swaps by Parity](https://leetcode.com/problems/largest-number-after-digit-swaps-by-parity)                                                 |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 2231 | [Largest Number After Digit Swaps by Parity](https://leetcode.com/problems/largest-number-after-digit-swaps-by-parity)                                                 |                                                                            [![Java](assets/java.png)](src/LargestNumberAfterDigitSwapsByParity.java)                                                                             |                                                                                                                                   |
 | 2235 | [Add Two Integers](https://leetcode.com/problems/add-two-integers)                                                                                                     |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2236 | [Root Equals Sum of Children](https://leetcode.com/problems/root-equals-sum-of-children)                                                                               |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2239 | [Find Closest Number to Zero](https://leetcode.com/problems/find-closest-number-to-zero)                                                                               |                                                                                                                                                                                                                                  |                                                                                                                                   |

Diff for: src/LargestNumberAfterDigitSwapsByParity.java

@@ -0,0 +1,49 @@
+// https://leetcode.com/problems/largest-number-after-digit-swaps-by-parity
+// T: O(log(n) log(log(n)))
+// S: O(log(n))
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+
+public class LargestNumberAfterDigitSwapsByParity {
+    public int largestInteger(int num) {
+        final String number = num + "";
+        final List<Integer> evenDigits = getEvenDigits(number);
+        final List<Integer> oddDigits = getOddDigits(number);
+
+        evenDigits.sort(Comparator.reverseOrder());
+        oddDigits.sort(Comparator.reverseOrder());
+
+        final StringBuilder result = new StringBuilder();
+        for (int i = 0, evenIndex = 0, oddIndex = 0; i < number.length() ; i++) {
+            if (isOddDigit(number, i)) {
+                result.append(oddDigits.get(oddIndex++));
+            } else {
+                result.append(evenDigits.get(evenIndex++));
+            }
+        }
+
+        return Integer.parseInt(result.toString());
+    }
+
+    private boolean isOddDigit(String number, int index) {
+        return (number.charAt(index) - '0') % 2 == 1;
+    }
+
+    private List<Integer> getEvenDigits(String string) {
+        final List<Integer> result = new ArrayList<>();
+        for (int index = 0 ; index < string.length() ; index++) {
+            if (!isOddDigit(string, index)) result.add(string.charAt(index) - '0');
+        }
+        return result;
+    }
+
+    private List<Integer> getOddDigits(String string) {
+        final List<Integer> result = new ArrayList<>();
+        for (int index = 0 ; index < string.length() ; index++) {
+            if (isOddDigit(string, index)) result.add(string.charAt(index) - '0');
+        }
+        return result;
+    }
+}