solves #2423: Remove Letter To Equalize Frequency in java

Author: anishLearnsToCode

README.md

@@ -769,7 +769,7 @@
 | 2409 | [Count Days Spent Together](https://leetcode.com/problems/count-days-spent-together)                                                                                   |                                                                                   [![Java](assets/java.png)](src/CountDaysSpentTogether.java)                                                                                    |                                                                                                                                   |
 | 2413 | [Smallest Even Multiple](https://leetcode.com/problems/smallest-even-multiple)                                                                                         |                                                                                    [![Java](assets/java.png)](src/SmallestEvenMultiple.java)                                                                                     |                                                                                                                                   |
 | 2418 | [Sort the People](https://leetcode.com/problems/sort-the-people)                                                                                                       |                                                                                        [![Java](assets/java.png)](src/SortThePeople.java)                                                                                        |                                                                                                                                   |
-| 2423 | [Remove Letter To Equalize Frequency](https://leetcode.com/problems/remove-letter-to-equalize-frequency)                                                               |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 2423 | [Remove Letter To Equalize Frequency](https://leetcode.com/problems/remove-letter-to-equalize-frequency)                                                               |                                                                               [![Java](assets/java.png)](src/RemoveLetterToEqualizeFrequency.java)                                                                               |                                                                                                                                   |
 | 2427 | [Number of Common Factors](https://leetcode.com/problems/number-of-common-factors)                                                                                     |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2432 | [The Employee That Worked on the Longest Task](https://leetcode.com/problems/the-employee-that-worked-on-the-longest-task)                                             |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 2437 | [Number of Valid Clock Times](https://leetcode.com/problems/number-of-valid-clock-times)                                                                               |                                                                                                                                                                                                                                  |                                                                                                                                   |

src/RemoveLetterToEqualizeFrequency.java

@@ -0,0 +1,52 @@
+// https://leetcode.com/problems/remove-letter-to-equalize-frequency
+// T: O(|word|)
+// S: O(1)
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+public class RemoveLetterToEqualizeFrequency {
+    public boolean equalFrequency(String word) {
+        final Map<Character, Integer> letterFrequency = getFrequencies(word);
+        final Map<Integer, Integer> numberFrequency = getFrequencies(letterFrequency.values());
+
+        if (letterFrequency.size() == 1) {
+            return true;
+        }
+
+        if (numberFrequency.size() == 1 && numberFrequency.keySet().iterator().next() == 1) {
+            return true;
+        }
+
+        if (numberFrequency.size() == 1 || numberFrequency.size() > 2) {
+            return false;
+        }
+
+        final Iterator<Integer> iterator = numberFrequency.keySet().iterator();
+        final int first = iterator.next(), second = iterator.next();
+        final int smallerNum = Math.min(first, second);
+        final int largerNum = Math.max(first, second);
+        final int smallerNumFreq = numberFrequency.get(smallerNum);
+        final int largerNumFreq = numberFrequency.get(largerNum);
+
+        return ((largerNum - smallerNum == 1) && largerNumFreq == 1) || (smallerNum == 1 && smallerNumFreq == 1);
+    }
+
+    private Map<Character, Integer> getFrequencies(String string) {
+        final Map<Character, Integer> result = new HashMap<>();
+        for (int index = 0 ; index < string.length() ; index++) {
+            char letter = string.charAt(index);
+            result.put(letter, result.getOrDefault(letter, 0) + 1);
+        }
+        return result;
+    }
+
+    private Map<Integer, Integer> getFrequencies(Iterable<Integer> iterable) {
+        final Map<Integer, Integer> result = new HashMap<>();
+        for (int value : iterable) {
+            result.put(value, result.getOrDefault(value, 0) + 1);
+        }
+        return result;
+    }
+}