2063. Vowels of All Substrings: RETRY, credit: https://leetcode.com/problems/vowels-of-all-substrings/solutions/5089523/functional-rust-solution/

Author: tan-wei

src/solution/mod.rs

@@ -1556,3 +1556,4 @@ mod s2058_find_the_minimum_and_maximum_number_of_nodes_between_critical_points;
 mod s2059_minimum_operations_to_convert_number;
 mod s2060_check_if_an_original_string_exists_given_two_encoded_strings;
 mod s2062_count_vowel_substrings_of_a_string;
+mod s2063_vowels_of_all_substrings;

src/solution/s2063_vowels_of_all_substrings.rs

@@ -0,0 +1,93 @@
+/**
+ * [2063] Vowels of All Substrings
+ *
+ * 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 <= 10^5
+ * 	word consists of lowercase English letters.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/vowels-of-all-substrings/
+// discuss: https://leetcode.com/problems/vowels-of-all-substrings/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    // Credit: https://leetcode.com/problems/vowels-of-all-substrings/solutions/5089523/functional-rust-solution/
+    pub fn count_vowels(word: String) -> i64 {
+        let n = word.len() as i64;
+        word.chars()
+            .enumerate()
+            .filter(|(i, c)| *c == 'a' || *c == 'e' || *c == 'i' || *c == 'o' || *c == 'u')
+            .map(|(i, c)| i as i64)
+            .fold(0i64, |acc, i| acc + (i + 1) * (n - i))
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2063_example_1() {
+        let word = "aba".to_string();
+
+        let result = 6;
+
+        assert_eq!(Solution::count_vowels(word), result);
+    }
+
+    #[test]
+    fn test_2063_example_2() {
+        let word = "abc".to_string();
+
+        let result = 3;
+
+        assert_eq!(Solution::count_vowels(word), result);
+    }
+
+    #[test]
+    fn test_2063_example_3() {
+        let word = "ltcd".to_string();
+
+        let result = 0;
+
+        assert_eq!(Solution::count_vowels(word), result);
+    }
+}