solves #2399: Check Distances Between Same Letters in java

Author: anishLearnsToCode

Diff for: README.md

@@ -764,7 +764,7 @@
 | 2383 | [Minimum Hours of Training to Win a Competition](https://leetcode.com/problems/minimum-hours-of-training-to-win-a-competition)                                         |                                                                           [![Java](assets/java.png)](src/MinimumHoursOfTrainingToWinACompetition.java)                                                                           |                                                                                                                                   |
 | 2389 | [Longest Subsequence With Limited Sum](https://leetcode.com/problems/longest-subsequence-with-limited-sum)                                                             |                                                                              [![Java](assets/java.png)](src/LongestSubsequenceWithLimitedSum.java)                                                                               |                                                                                                                                   |
 | 2395 | [Find Subarrays With Equal Sum](https://leetcode.com/problems/find-subarrays-with-equal-sum)                                                                           |                                                                                  [![Java](assets/java.png)](src/FindSubarraysWithEqualSum.java)                                                                                  |                                                                                                                                   |
-| 2399 | [Check Distances Between Same Letters](https://leetcode.com/problems/check-distances-between-same-letters)                                                             |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 2399 | [Check Distances Between Same Letters](https://leetcode.com/problems/check-distances-between-same-letters)                                                             |                                                                              [![Java](assets/java.png)](src/CheckDistancesBetweenSameLetters.java)                                                                               |                                                                                                                                   |
 | 2404 | [Most Frequent Even Element](https://leetcode.com/problems/most-frequent-even-element)                                                                                 |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2409 | [Count Days Spent Together](https://leetcode.com/problems/count-days-spent-together)                                                                                   |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2413 | [Smallest Even Multiple](https://leetcode.com/problems/smallest-even-multiple)                                                                                         |                                                                                                                                                                                                                                  |                                                                                                                                   |

Diff for: src/CheckDistancesBetweenSameLetters.java

@@ -0,0 +1,22 @@
+// https://leetcode.com/problems/check-distances-between-same-letters
+// T: O(N)
+// S: O(1)
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class CheckDistancesBetweenSameLetters {
+    public boolean checkDistances(String s, int[] distances) {
+        final Map<Character, Integer> firstOccurrenceIndex = new HashMap<>();
+        for (int index = 0 ; index < s.length() ; index++) {
+            char letter = s.charAt(index);
+            if (firstOccurrenceIndex.containsKey(letter)) {
+                int distance = index - firstOccurrenceIndex.get(letter) - 1;
+                if (distance != distances[letter - 'a']) {
+                    return false;
+                }
+            } else firstOccurrenceIndex.put(letter, index);
+        }
+        return true;
+    }
+}