LeetCode-in-Java
2063. Vowels of All Substrings
Medium
Given a string word, return the sum of the number of vowels ('a', 'e', 'i', 'o', and 'u') in every substring of word.
A substring is a contiguous (non-empty) sequence of characters within a string.
Note: Due to the large constraints, the answer may not fit in a signed 32-bit integer. Please be careful during the calculations.
Example 1:
Input: word = “aba”
Output: 6
Explanation: All possible substrings are: “a”, “ab”, “aba”, “b”, “ba”, and “a”.
-
“b” has 0 vowels in it
-
“a”, “ab”, “ba”, and “a” have 1 vowel each
-
“aba” has 2 vowels in it
Hence, the total sum of vowels = 0 + 1 + 1 + 1 + 1 + 2 = 6.
Example 2:
Input: word = “abc”
Output: 3
Explanation: All possible substrings are: “a”, “ab”, “abc”, “b”, “bc”, and “c”.
-
“a”, “ab”, and “abc” have 1 vowel each
-
“b”, “bc”, and “c” have 0 vowels each
Hence, the total sum of vowels = 1 + 1 + 1 + 0 + 0 + 0 = 3.
Example 3:
Input: word = “ltcd”
Output: 0
Explanation: There are no vowels in any substring of “ltcd”.
Constraints:
1 <= word.length <= 105wordconsists of lowercase English letters.
Solution
public class Solution {
public long countVowels(String word) {
long ans = 0;
for (int i = 0; i < word.length(); i++) {
if (isVowel(word.charAt(i))) {
long right = word.length() - (long) i - 1;
ans += ((long) i + 1) * (right + 1);
}
}
return ans;
}
private boolean isVowel(char ch) {
return ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u';
}
}