1941. Check if All Characters Have Equal Number of Occurrences: AC

Author: tan-wei

Diff for: src/solution/mod.rs

@@ -1462,3 +1462,4 @@ mod s1935_maximum_number_of_words_you_can_type;
 mod s1936_add_minimum_number_of_rungs;
 mod s1937_maximum_number_of_points_with_cost;
 mod s1938_maximum_genetic_difference_query;
+mod s1941_check_if_all_characters_have_equal_number_of_occurrences;

Diff for: src/solution/s1941_check_if_all_characters_have_equal_number_of_occurrences.rs

@@ -0,0 +1,72 @@
+/**
+ * [1941] Check if All Characters Have Equal Number of Occurrences
+ *
+ * Given a string s, return true if s is a good string, or false otherwise.
+ * A string s is good if all the characters that appear in s have the same number of occurrences (i.e., the same frequency).
+ *  
+ * Example 1:
+ *
+ * Input: s = "abacbc"
+ * Output: true
+ * Explanation: The characters that appear in s are 'a', 'b', and 'c'. All characters occur 2 times in s.
+ *
+ * Example 2:
+ *
+ * Input: s = "aaabb"
+ * Output: false
+ * Explanation: The characters that appear in s are 'a' and 'b'.
+ * 'a' occurs 3 times while 'b' occurs 2 times, which is not the same number of times.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= s.length <= 1000
+ * 	s consists of lowercase English letters.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/check-if-all-characters-have-equal-number-of-occurrences/
+// discuss: https://leetcode.com/problems/check-if-all-characters-have-equal-number-of-occurrences/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn are_occurrences_equal(s: String) -> bool {
+        let hm: std::collections::HashMap<char, u32> =
+            s.chars()
+                .fold(std::collections::HashMap::new(), |mut hm, c| {
+                    *hm.entry(c).or_insert(0) += 1;
+                    hm
+                });
+
+        let expected: &u32 = hm.get(&s.chars().next().unwrap()).unwrap();
+
+        hm.iter().all(|(_, count)| count == expected)
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1941_example_1() {
+        let s = "abacbc".to_string();
+
+        let result = true;
+
+        assert_eq!(Solution::are_occurrences_equal(s), result);
+    }
+
+    #[test]
+    fn test_1941_example_2() {
+        let s = "aaabb".to_string();
+
+        let result = false;
+
+        assert_eq!(Solution::are_occurrences_equal(s), result);
+    }
+}