cs: add «2270. Number of Ways to Split Array»

URL:	https://leetcode.com/problems/number-of-ways-to-split-array/
Signed-off-by: Matej Focko <me@mfocko.xyz>

cs/number-of-ways-to-split-array.cs

@@ -0,0 +1,17 @@
+public class Solution {
+    public int WaysToSplitArray(int[] nums) {
+        var (leftSum, rightSum) = (0l, nums.Select(x => (long)x).Sum());
+
+        var count = 0;
+        for (var i = 0; i < nums.Length - 1; ++i) {
+            leftSum += nums[i];
+            rightSum -= nums[i];
+
+            if (leftSum >= rightSum) {
+                ++count;
+            }
+        }
+
+        return count;
+    }
+}