solves count vowel substrings of a string

Author: anishLearnsToCode

README.md

@@ -490,7 +490,7 @@
 | 2047 | [Number of Valid Words in a Sentence](https://leetcode.com/problems/number-of-valid-words-in-a-sentence)                                                  |                                                          [![Java](assets/java.png)](src/NumberOfValidWordsInASentence.java)                                                          |                                                                                                                                   |
 | 2053 | [Kth Distinct String in an Array](https://leetcode.com/problems/kth-distinct-string-in-an-array)                                                          |                                                           [![Java](assets/java.png)](src/KthDistinctStringInAnArray.java)                                                            |                                                                                                                                   |
 | 2057 | [Smallest Index With Equal Value](https://leetcode.com/problems/smallest-index-with-equal-value)                                                          |                                                           [![Java](assets/java.png)](src/SmallestIndexWithEqualValue.java)                                                           |                                                                                                                                   |
-| 2062 | [Count Vowel Substrings of a String](https://leetcode.com/problems/count-vowel-substrings-of-a-string)                                                    |                                                                                                                                                                                      |                                                                                                                                   |
+| 2062 | [Count Vowel Substrings of a String](https://leetcode.com/problems/count-vowel-substrings-of-a-string)                                                    |                                                          [![Java](assets/java.png)](src/CountVowelSubstringsOfAString.java)                                                          |                                                                                                                                   |
 | 2068 | [Check Whether Two Strings are Almost Equivalent](https://leetcode.com/problems/check-whether-two-strings-are-almost-equivalent)                          |                                                                                                                                                                                      |                                                                                                                                   |
 | 2073 | [Time Needed to Buy Tickets](https://leetcode.com/problems/time-needed-to-buy-tickets)                                                                    |                                                                                                                                                                                      |                                                                                                                                   |
 | 2078 | [Two Furthest Houses With Different Colors](https://leetcode.com/problems/two-furthest-houses-with-different-colors)                                      |                                                                                                                                                                                      |                                                                                                                                   |

src/CountVowelSubstringsOfAString.java

@@ -0,0 +1,51 @@
+// https://leetcode.com/problems/count-vowel-substrings-of-a-string
+// T: O(|word|)
+// S: O(|word|)
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+public class CountVowelSubstringsOfAString {
+    private static final Set<Character> VOWELS = Set.of('a', 'e', 'i', 'o','u');
+
+    public static int countVowelSubstrings(String word) {
+        int vowelSubstrings = 0;
+        final Map<Character, Integer> vowels = new HashMap<>();
+        for (int j = 0 ; j < word.length() ; j++) {
+            if (isVowel(word.charAt(j))) {
+                addToMap(vowels, word.charAt(j));
+                for (int i = j + 1, k = j ; i < word.length() ; i++) {
+                    if (isVowel(word.charAt(i))) {
+                        addToMap(vowels, word.charAt(i));
+                        for ( ; k < i && vowels.size() == 5 ; k++) {
+                            removeFromMap(vowels, word.charAt(k));
+                        }
+                        vowelSubstrings += k - j;
+                        if (i == word.length() - 1) {
+                            j = i;
+                        }
+                    } else {
+                        j = i;
+                        vowels.clear();
+                        break;
+                    }
+                }
+            }
+        }
+        return vowelSubstrings;
+    }
+
+    private static boolean isVowel(char c) {
+        return VOWELS.contains(c);
+    }
+
+    private static void addToMap(Map<Character, Integer> frequencies, char c) {
+        frequencies.put(c, frequencies.getOrDefault(c, 0) + 1);
+    }
+
+    private static void removeFromMap(Map<Character, Integer> frequencies, char c) {
+        if (frequencies.getOrDefault(c, 0) == 1) frequencies.remove(c);
+        else frequencies.put(c, frequencies.get(c) - 1);
+    }
+}