Added 0523-continuous-subarray-sum.cs

Author: Dalton-V

csharp/0523-continuous-subarray-sum.cs

@@ -0,0 +1,21 @@
+using System.Collections.Generic;
+
+public class Solution
+{
+    public bool CheckSubarraySum(int[] nums, int k)
+    {
+        var remainder = new Dictionary<int, int>();
+        remainder.Add(0, -1);
+        var total = 0;
+        for (var i = 0; i < nums.Length; i++)
+        {
+            total += nums[i];
+            var r = total % k;
+            if (!remainder.ContainsKey(r))
+                remainder.Add(r, i);
+            else if (i - remainder[r] > 1)
+                return true;
+        }
+        return false;
+    }
+}