cs: add «2554. Maximum Number of Integers to Choose From a Range I»

URL:	https://leetcode.com/problems/maximum-number-of-integers-to-choose-from-a-range-i/
Signed-off-by: Matej Focko <me@mfocko.xyz>

cs/maximum-number-of-integers-to-choose-from-a-range-i.cs

@@ -0,0 +1,20 @@
+public class Solution {
+    public int MaxCount(int[] banned, int n, int maxSum) {
+        Array.Sort(banned);
+
+        int idx = 0, used = 0;
+        for (int i = 1; i <= n && maxSum > 0; ++i) {
+            var skip = idx < banned.Length && banned[idx] == i;
+            while (idx < banned.Length && banned[idx] == i) {
+                ++idx;
+            }
+
+            if (!skip && maxSum - i >= 0) {
+                maxSum -= i;
+                ++used;
+            }
+        }
+
+        return used;
+    }
+}