1781. Sum of Beauty of All Substrings: AC

src/solution/mod.rs

@@ -1342,3 +1342,4 @@ mod s1775_equal_sum_arrays_with_minimum_number_of_operations;
 mod s1776_car_fleet_ii;
 mod s1779_find_nearest_point_that_has_the_same_x_or_y_coordinate;
 mod s1780_check_if_number_is_a_sum_of_powers_of_three;
+mod s1781_sum_of_beauty_of_all_substrings;

src/solution/s1781_sum_of_beauty_of_all_substrings.rs

@@ -0,0 +1,89 @@
+/**
+ * [1781] Sum of Beauty of All Substrings
+ *
+ * The beauty of a string is the difference in frequencies between the most frequent and least frequent characters.
+ *
+ * 	For example, the beauty of "abaacc" is 3 - 1 = 2.
+ *
+ * Given a string s, return the sum of beauty of all of its substrings.
+ *  
+ * Example 1:
+ *
+ * Input: s = "aabcb"
+ * Output: 5
+ * Explanation: The substrings with non-zero beauty are ["aab","aabc","aabcb","abcb","bcb"], each with beauty equal to 1.
+ * Example 2:
+ *
+ * Input: s = "aabcbaa"
+ * Output: 17
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= s.length <=^ 500
+ * 	s consists of only lowercase English letters.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/sum-of-beauty-of-all-substrings/
+// discuss: https://leetcode.com/problems/sum-of-beauty-of-all-substrings/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn beauty_sum(s: String) -> i32 {
+        let s = s.chars().collect::<Vec<char>>();
+        let n = s.len();
+        let mut memo = vec![vec![0; 26]; n + 1];
+
+        for i in 0..n {
+            memo[i + 1] = memo[i].clone();
+            memo[i + 1][s[i] as usize - 'a' as usize] += 1;
+        }
+
+        let mut result = 0;
+        for i in 0..n {
+            for j in i..n {
+                let mut max = 0;
+                let mut min = n + 10;
+
+                for k in 0..26 {
+                    let v = memo[j + 1][k] - memo[i][k];
+                    max = max.max(v);
+                    if v != 0 {
+                        min = min.min(v);
+                    }
+                }
+                result += max - min;
+            }
+        }
+
+        result as i32
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1781_example_1() {
+        let s = "aabcb".to_string();
+
+        let result = 5;
+
+        assert_eq!(Solution::beauty_sum(s), result);
+    }
+
+    #[test]
+    fn test_1781_example_2() {
+        let s = "aabcbaa".to_string();
+
+        let result = 17;
+
+        assert_eq!(Solution::beauty_sum(s), result);
+    }
+}