https://leetcode.com/problems/happy-number/

Author: harshitgindra

EasyProblems/HappyNumber.cs

@@ -0,0 +1,51 @@
+namespace LeetCode.EasyProblems;
+
+public class HappyNumber
+{
+    public bool IsHappy(int n)
+    {
+        HashSet<int> visitedNumbers = new HashSet<int>();
+
+        while (n != 1)
+        {
+            // Detect cycle - if we've seen this number before
+            if (!visitedNumbers.Add(n))
+                return false;
+
+            n = SumOfSquares(n);
+        }
+
+        return true;
+    }
+
+    private static int SumOfSquares(int n)
+    {
+        int sum = 0;
+        while (n > 0)
+        {
+            int digit = n % 10;
+            sum += digit * digit;
+            n /= 10; // Remove last digit
+        }
+
+        return sum;
+    }
+
+    [Test(Description = "https://leetcode.com/problems/happy-number/")]
+    [Category("Easy")]
+    [Category("LeetCode")]
+    [Category("Happy Number")]
+    [TestCaseSource(nameof(Input))]
+    public void Test1((bool Output, int Input) item)
+    {
+        var response = IsHappy(item.Input);
+        Assert.That(response, Is.EqualTo(item.Output));
+    }
+
+    public static IEnumerable<(bool Output, int Input)> Input =>
+        new List<(bool Output, int Input)>()
+        {
+            (true, 19),
+            (false, 2),
+        };
+}