#1941: Check if All Characters Have Equal Number of Occurrences; solution & tests

Author: vetalapo

c-sharp/Problems/arrays-and-hashing/CheckIfAllCharactersHaveEqualNumberOfOccurrences.cs

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+/**
+ * 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.
+ *
+ * Hint 1:
+ *   Build a dictionary containing the frequency of each character appearing in s
+ *
+ * Hint 2:
+ *   Check if all values in the dictionary are the same.
+ **
+ * https://leetcode.com/problems/check-if-all-characters-have-equal-number-of-occurrences/
+***/
+
+namespace Problems;
+
+public class CheckIfAllCharactersHaveEqualNumberOfOccurrences
+{
+    public bool AreOccurrencesEqual( string s )
+    {
+        int[] freqMap = new int[26];
+
+        foreach ( char c in s )
+        {
+            freqMap[c - 'a']++;
+        }
+
+        int firstElementFrequency = freqMap[s[0] - 'a'];
+
+        foreach ( int freq in freqMap )
+        {
+            if ( freq != 0 && freq != firstElementFrequency )
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}

c-sharp/Tests/arrays-and-hashing/CheckIfAllCharactersHaveEqualNumberOfOccurrencesTests.cs

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+using NUnit.Framework;
+
+using Problems;
+
+public class CheckIfAllCharactersHaveEqualNumberOfOccurrencesTests
+{
+    [TestCase( "abacbc", ExpectedResult = true )]
+    [TestCase( "aaabb", ExpectedResult = false )]
+    [TestCase( "vvvvvvvvvvvvvvvvvvv", ExpectedResult = true )]
+    public bool AreOccurrencesEqualTest( string s ) =>
+        new CheckIfAllCharactersHaveEqualNumberOfOccurrences().AreOccurrencesEqual( s );
+}